Vietnamese Heritage Language: From Silence to Voice

Abstract

Immigration and emigration shape unique language contact environments and multilingual settings, intertwined with language ideologies, attitudes, practices, and the emergence of new contact languages. Heritage languages, spoken by immigrant children or individuals who migrated at a young age, have garnered attention, particularly in the United States and Canada since the 1960s and 1970s, and later in Europe and elsewhere. However, despite approximately 4 million individuals with Vietnamese immigration backgrounds worldwide, research on the Vietnamese language has only spanned since the 2000s. This review assesses the current state of Vietnamese heritage language studies, identifying topics explored, their development, existing gaps, and potential research directions. It synthesizes diverse findings, highlighting recent focus areas on heritage language loss, maintenance, ideology, education, proficiency assessment, and linguistic characteristics. The review identifies limitations in existing literature and offers recommendations for addressing them.

Heritage Language and Vietnamese Heritage Language: Term and Principle

Ngoc Müller-Tran holds a Ph.D. in education studies and serves as the director of a cultural program in Germany designed for individuals with immigrant backgrounds. She arrived in Germany at the age of five, along with her parents, who were both contract workers. Nga Schwenke, an IT professional, also arrived in Germany at the age of five, the same as Ngoc. While Ngoc bears a Vietnamese first name and a surname that blends Vietnamese and German heritage from her husband, Nga opted to relinquish her original Vietnamese surname after her marriage. Both Ngoc and Nga belong to the 1.5 generation of Vietnamese immigrants.

Ngoc possesses a strong command of the Vietnamese language, having pursued additional Vietnamese language courses in school and even selecting Vietnamese as a subsidiary subject during her university studies. She has a deep affinity for the Vietnamese language and culture, actively passing on her knowledge to her child. Occasionally, she encounters challenges in formal writing, however her current time constraints limit her pursuit of further improvement. Conversely, Nga exhibits proficiency in understanding and speaking Vietnamese, but her writing skills remain underdeveloped. Consequently, she enrolls in a virtual Vietnamese class for overseas Vietnamese. Nga welcomes the opportunity to delve into the intricacies of this heritage language and culture, as it allows her to engage in discussions about music and poetry with her Vietnamese language teacher.

Ngan Ha Nguyen, an eight-year-old born in Germany, retains her pure Vietnamese name, which poses a challenge for her teachers and friends when attempting to pronounce it correctly in her native language. Nevertheless, this does not hinder her effective communication within her school environment, as she converses fluently in Vietnamese with her mother at home. Additionally, she contacts her grandparents in Vietnam every weekend, further solidifying her grasp of the language. While she can read Vietnamese to some extent, writing remains a significant challenge due to the absence of Vietnamese language classes in her school system. She doesn't dwell on this issue, however her mother has plans to provide her with additional instruction at home.

Harry Tran, a nine-year-old born in Germany, comprehends Vietnamese well but struggles with both speaking and writing in the language . He shows reluctance to use Vietnamese and adamantly refuses to attend Vietnamese weekend classes.

Danny Schöning has a Vietnamese mother and a German father. He converses in Vietnamese with a slight German accent and is currently enrolled in a virtual Vietnamese class due to his mother's insistence. Initially resistant, he has grown more comfortable and now actively participates in discussions in Vietnamese within the class.

These life stories, exemplified by Ngoc, Nga, Ngan Ha, Harry, and Danny, resonate not only in Germany but also in many other countries with immigrant communities. The choices they make regarding their names, either self-selected or given by their parents, can influence their connection to their heritage language and culture. These individuals exhibit a spectrum of proficiency in Vietnamese, ranging from limited understanding like Harry and Danny, to greater proficiency demonstrated by Ngoc and Nga. Numerous factors contribute to their heritage language proficiency and motivation for its maintenance.

These individuals, along with millions of others who share similarly diverse life experiences, are collectively referred to as heritage speakers of Vietnamese. According to the Ministry of Foreign Affairs in Vietnam (2012), Vietnamese is spoken in the homes of approximately four million individuals residing outside Vietnam, making it a significant subject of interest in linguistic, cultural, and educational research.

The Vietnamese language is one of many heritage languages outside borders of origin countries. The term heritage language appeared in educational research on the acquisition of languages other than English and French by bilingual students in Canada in the 1970s. Later, in the late 1990s, this term was broadly used in the United States to refer to ethno-cultural languages (Cummins, 1983, p. 7; Cummins, 2005, p. 585). Heritage languages may include immigrant languages (e.g., German in the United States, Vietnamese in Germany), national minority languages (e.g., Basque in Spain, Hmong in Vietnam), and aboriginal languages (e.g., Navajo in the United States, Dyirbal in Australia). More precisely, Rothman (2009, p. 156) defines a heritage language as follows:

A language qualifies as a heritage language if it is a language spoken at home or otherwise readily available to young children, and crucially this language is not a dominant language in the larger (national) society. Like the acquisition of a primary language in monolingual situations and the acquisition of two or more languages in situations of societal bilingualism/multilingualism, the heritage language is acquired on the basis of an interaction with naturalistic input and whatever in-born linguistic mechanisms are at play in any instance of child language acquisition. Differently, however, there is the possibility that quantitative and qualitative differences in heritage language input and the introduction, influence of the societal majority language, and differences in literacy and formal education can result in what on the surface seems to be arrested development of the heritage language or attrition in adult bilingual knowledge. (Italics in the original)

Other commonly used terms to refer to the heritage language of bilinguals are first language (L1), mother tongue, ancestral language, ethnic language, third language, non-official language, etc. (Cummins, 1983, p. 7; Montrul, 2016, p. 13).

In many countries, especially in the United States and Europe, languages other than the official language are often considered “foreign” languages. Nevertheless, these languages are not “foreign” to many individuals or communities because many people who live in those countries have cultural connections to them and know languages other than the official ones (Cummins, 1983). Whether these people have a high proficiency in these languages or cannot understand them, they always belong to a family or a community where the language is used (Montrul, 2016). Kelleher (2010, p. 1) emphasizes: “The term ‘heritage’ language can be used to describe any of these connections between a non-dominant language and a person, a family, or a community”. The literal meaning of the term heritage language already expresses the connection of the immigrant group with the home country and the language of their country of origin.

In Germany, the term Herkunftsprache (heritage language) has been used in studies on multilinguals and multilingualism since the early 2000s (Flores & Rinke, 2016, p. 22) to define the special acquisition conditions of a minority language in the context of migration. Reich (2009, p. 445) defined “Herkunftsprache” (language of origin) to be migrants bring their mother tongues to other immigration countries (“Migranten als ihre Muttersprachen in anderssprachige Einwanderungsländer mitbringen”). However, Fürstenau (2011, p. 31) criticized the term “Herkunfsprache” because the regional origin does not always imply the actual language used, for example, there is a sharp separation between the Turkish populations due to their 40 minority languages (Brizić, 2006, p. 36). In addition, the language of an emigrated group may differ from the language used in the country of origin (Lüttenberg, 2010, p. 306). For these reasons, in studies on the language of origin of migrants, the terms “Muttersprache” (mother tongue), “Erstsprache” (first language), and “Familiensprache” (family language) have often been used in Germany despite their differently potential meanings, which can include the language that was first acquired, the language that is frequently used in everyday communication, the language that is used fluently, the language that was preferred, or the language that can link migrants with their specific cultural affiliation (König, 2016, p. 286; Lüttenberg, 2010, p. 307).  Meanwhile, the English term “heritage language” refers to the connection between the migrants with their home culture and language (König, 2016, p. 286).

In studies on the Vietnamese language of immigrants in different countries, the term heritage language may have been first used to refer to the Vietnamese language in the United States in the study of Maloof et al. (2006). Some other studies related to the Vietnamese language of Vietnamese immigrants around the world also utilize this term (Nguyen, 2020; Phan, 2017, 2018; Tran, 2018, 2019). Many different terms have been used to refer to the Vietnamese language abroad, for example, home language (Tran et al., 2021a), first language (Nguyen et al., 2001), and immigrant language (Zhou & Bankston, 1998). The present study uses the term heritage language to refer to the Vietnamese language of immigrants abroad to express the connection between Vietnamese migrants and their home culture and language (König, 2016).

Heritage Language Studies: From the Margins to a Central Focus

Nowadays, thanks to the so-called “social turn”, “the acquisition of heritage languages has moved from the margins to become a central focus of study within linguistics and applied linguistics” (Montrul, 2016, p. 6; Page & Putnam, 2015). While only a few European languages such as Spanish and German heritage languages in the United States were extensively investigated in the last decades, there has recently been a series of publications concerning Asian languages such as Korean, Japanese, and Chinese (He & Xiao, 2008; Lee, 2002; Mu, 2015; Zhang & Slaughter-Defoe, 2009). In addition, the list of dissertations on heritage language education from 2000–2012 by the Alliance for the Advancement of Heritage Languages, Center of Applied Linguistics, impartially supplies evidence for this trend. Moreover, the Heritage Language Journal (HLJ) was released in 2002 to provide a forum for researchers to exchange research results and knowledge about heritage languages.

The dramatic change in research on heritage languages may have emerged from the argument of language as a resource since 2001 (Nguyen et al., 2001). The benefits of multilingualism for individuals and societies are manifold, including the realms of intellectual life, culture, family, and economy. Lo Bianco (2017, p. 65) argues that multilingualism benefits cultural diversity for both entire societies and minority communities, due to the increase intercultural understanding through learning and practicing languages. Multilingualism, especially the maintenance of heritage languages, entails strong intergenerational ties for immigrants who can benefit substantially in terms of health and psychological development, such as sharing emotions and maintaining the authority of parents and caregivers. Aiko (2017, p. 106) states that learning heritage languages and cultures helps heritage speakers gain a sense of belonging, which supports a positive sense of identity and the development of self-confidence. Therefore, heritage language use encourages learners to transmit their own cultures from one generation to the next. However, it is very difficult to maintain a language and a culture in an inappropriate educational context. A question that emerges in this context is to what extent the maintenance of a heritage language should or can be encouraged, for example, by organizing a formal learning environment or offering interesting learning activities.

One of the most widely studied topics of heritage language concerns the attitude of heritage speakers towards the maintenance of a heritage language from different perspectives, because “language attitudes are collectively historically shaped and can also be politically co-determined” (Franceschini, 2011, p. 346). Attitudes are considered “powerful variables” (ibid., 346) that co-govern the development of multilingual language use. Numerous studies have investigated the attitude towards heritage language from parents’ perspectives (Nesteruk, 2010; Tran et al., 2021a; Zhang & Slaughter-Defoe, 2009), teachers’ perspectives (Cummins, 2001; Liu, 2006; Rodríguez, 2007), and students’ points of view (Liao et al., 2017; Oh & Nash, 2014). Cummins (2001) noted that international students enrolled at the University of Toronto (Canada) frequently complained about their elementary school children rejecting their home language and culture. Many children refuse to use the first language at home and want to anglicize their names in order to belong to the culture of the school and peer group. In the case of immigrant parents with a low proficiency in the languages of host countries, the rejection of the home language of children and adolescents often leads to parent–child conflicts, decreased levels of parental authority, and overall family cohesion issues (Chapman & Perreira, 2005; Driscoll & Torres, 2013). However, the attitude of heritage speakers may change in the course of their lifespans. For example, in a study on Chinese heritage language, Mu (2015) cited a statement by an Australian-Chinese young adult:

I am completely lost. I am struggling with my belongingness. I am different in Australia because I look Chinese. I am also different here because I look Chinese but I can’t speak Chinese. I wish I had learned (Chinese) harder when I was in Saturday schools.

(Mu, 2015: xxi)

Regarding the educational perspective, all bilingual programs in the United States and Canada function very well and have proved that children can acquire two languages well at the same time (Cummins, 2001, p. 10). Therefore, there has been an increasingly large number of studies on heritage language education (e.g., Cummins, 2001; Nguyen et al., 2001). However, heritage language instruction has still been considered similar to foreign language teaching (Fishman, 2001; Valdés, 2001). The need to develop new programs and pedagogical materials to address the specific requirements of heritage speakers has been shared by many language practitioners (Brinton et al., 2008). Learning a heritage language is a necessary right for all learners, because it can be a resource for individuals and society (Busch, 2011, p. 544). One of many new pedagogical approaches that have been  approved is service learning (Moreno & MacGregor-Mendoza, 2017, p. ii). Heritage language studies has become a central focus in linguistics and social studies in the last two decades (Montrul, 2016, p. 45).

As per Boom and Polinsky (2014), despite heritage language research being a relatively new field, it has garnered significant attention due to its relevance in today's multicultural society. Consequently, heritage languages have become a subject of exploration across various disciplines. This inquiry ultimately equips heritage speakers, often accustomed to linguistic silence in their first language, with the tools to bridge the gap from silence to expression. Heritage language research grants these individuals a new voice, enabling them to become truly bilingual and bicultural (p. 17).

The concept of transitioning from “silence to voice” (Boom and Polinsky, 2014) serves as an inspiration for delving into Vietnamese heritage language research. This endeavor seeks to understand the scope of studies in this field, assess their level of establishment, identify existing gaps, and determine potential directions for future research. Such a review can shed light on the voices of heritage speakers, offering insights into their experiences growing up with the Vietnamese heritage language in Western countries across various aspects of life.

Vietnamese Heritage Language—Common Research Topics in Western Countries

Despite the significant presence of approximately 4 million individuals with Vietnamese immigration backgrounds worldwide (Ministry of Foreign Affairs Vietnam, 2012), research on the Vietnamese heritage language has yet to transition “from margins to a central focus” as observed with other heritage languages (Montrul, 2016, p. 45). In a comprehensive study by Wiley et al. (2014), spanning 300 years of heritage language research in the United States, Vietnamese received only cursory mentions within statistical tables, such as those detailing the most commonly spoken languages at home among different age groups (“Language other than English most commonly spoken at home” (2005–2009; 2010–2011), and “Language most commonly spoken at home for 5–18 year olds” (2007–2011)). Although ranking seventh, sixth, and fifth in importance in these tables, the Vietnamese heritage language did not receive a dedicated section. However, research on this heritage language has been ongoing for over two decades in Western countries. This paper aims to provide an overview of common themes in the literature on the Vietnamese heritage language, particularly in the United States, Australia, and Europe.

As previously mentioned, the study of Vietnamese heritage language emerged in the United States in the early twenty-first century. In recent times, research on Vietnamese heritage language has extended to various host countries. Table 7.1 outlines the prevailing themes in research within this field.

Table 7.1 Studies on Vietnamese heritage language

Table 7.1 illustrates that research on the Vietnamese heritage language commenced approximately two decades ago. Notably, many of the authors conducting these studies possess names that suggest Vietnamese origins. Since its inception, this field has consistently explored different facets and perspectives of the language, with a gradual upward trend in research activity over time. Figure 7.1 visually depicts the evolving research trends within the realm of the Vietnamese heritage language.

Fig. 7.1

Number of research on Vietnamese heritage language in Western countries over the last two decades

Figure 7.1 presents a clear trajectory of the evolving landscape of research on Vietnamese heritage language. Notably, in recent years, particularly since 2011, there has been a noticeable increase in both the quantity and regularity of studies within this field. On average, 2.6 publications related to this topic have appeared each year. This trend signals a positive and growing interest in gaining a deeper understanding of Vietnamese heritage language.

The study of Vietnamese heritage language has witnessed significant growth and development over the past two decades. Originating primarily in the United States, this field has expanded to encompass various host countries, reflecting a broader global interest in understanding and preserving this cultural and linguistic heritage. The increasing number of publications in recent years, averaging 2.6 per annum since 2011, underscores the growing significance and commitment to exploring different facets of Vietnamese heritage language. In Asia, such as in Japan and Taiwan, studies on Vietnamese as a heritage language or an inherited language have also started to gain more attention (Yu-ching et al., 2015; Đỗ, 2023). This research trend bodes well for enriching our comprehension of this unique language and its role within diverse diaspora communities around the world. As studies continue to evolve and expand, they contribute to bridging the gap between silence and voice for heritage language speakers, empowering them to embrace their bilingual and bicultural identities.

Following are the main topics of research on Vietnamese heritage language up to date.

Vietnamese Heritage Language Loss and Shift

The topic of language loss and shift has been studied earlier than other topics and primarily introduced by Zhou (2001) in the United States. She designed a study with 363 Vietnamese teenagers in San Diego, using questionnaires and self-reports. This study revealed a crucial aspect of language loss and shift: the timeline of change. The result indicated a decline in the use of Vietnamese heritage language among Vietnamese youths aged 14, with English proficiency increasing inversely to the decline in Vietnamese heritage language literacy skills.

Another study in the United States, Maloof et al. (2006) argued that Vietnamese heritage language loss usually occurs within 1.5–2 generations of residing in this country. The convincing evidence for this loss is that only 15% of participants who belong to the second generation still use Vietnamese with siblings. Further evidence for this argument comes from the experience of many people living in the United States. During the high school years, Andrew, a Vietnamese-American writer, lost his grasp on Vietnamese (Lam, 2005). “Mouthfuls of consonants began to reform his tongue, his teeth, his lips” (ibid., p. ix). Despite writing many books about hisVietnamese and American worlds, he used only English, the language that gave him confidence to write.

Pham (2011) collected Vietnamese and English data from Vietnamese bilinguals in the United States at four different times to examine the language change of this target group. The results showed that one of the two languages of the children at school-age time grew positively. Particularly, during the middle childhood, the dominant language shifted from the L1 (i.e., Vietnamese) to the L2 (i.e., English) (p. 67).

Despite being an important home language of about 300,000 speakers in Australia, Vietnamese is reported to be lost among the second and third generations (Tran et al. 2021a). Verdon et al. (2014) conducted a longitudinal study with 4252 young children from different immigration backgrounds to identify patterns of language maintenance and loss. The loss of other languages than English (heritage languages) including Vietnamese heritage language occurred over the first five years of life regularly. Between 3 waves (0–1 year, 2–3 years, 4–5 years), the maintenance of speaking heritage languages decreased to 86.6%.

In summary, while there is a body of research on Vietnamese heritage language loss and shift, its scope remains relatively limited, especially considering the various ages and circumstances in which these changes occur. Existing studies have primarily focused on identifying the timeline of language loss, but it is essential to acknowledge that these dynamics are influenced by a multitude of environmental and personal factors, including parental language use, family language policies, cultural connections, and language learning (Verdon et al., 2014; Tran et al. 2021b). A comprehensive understanding of these intricate dynamics is crucial for addressing heritage language preservation challenges effectively.

The findings of collected publications revealed a decline in Vietnamese heritage language proficiency among Vietnamese heritage speakers, with an inverse relationship observed between the decrease in Vietnamese literacy skills and an increase in English proficiency. It brings “a voice” refers to the capacity or ability of Vietnamese heritage language speakers to use and maintain their language skills, specifically their proficiency in Vietnamese, amidst the influence of English proficiency. The decline in Vietnamese language proficiency represents a weakening or loss of “the voice” of the Vietnamese heritage language within this population.

Vietnamese Heritage Language Maintenance

The loss and transformation of heritage language within diasporic communities can vary based on individual perspectives and the attitudes of parents of heritage language speakers towards the preservation of the Vietnamese heritage language. This particular aspect has been a focal point of research within the field of Vietnamese heritage language studies, as evident in Table 7.1. Pioneering studies by Young and Tran (1999) and Nguyen et al. (2001) represent early efforts to explore these attitudes regarding the Vietnamese heritage language. In their research involving 588 first- to eighth-grade students of Vietnamese descent in California, United States, and relying on self-reports, Nguyen et al. (2001) reported that a majority of participants (80%) emphasized the significance of preserving their Vietnamese culture and language. Furthermore, 91% of these students deemed learning Vietnamese in school as highly important, with 67% expressing a strong desire to receive formal Vietnamese language education in school settings.

In addition, the findings showed that there is a correlation between the high levels of spoken Vietnamese competence, as well as the high levels of communication with parents of heritage language speakers in this heritage language, and English competence. First-language use is, therefore, not detrimental to the development of spoken English. Additionally, the correlation between English literacy and self-reported competence in Vietnamese was close to zero, indicating that there is no evidence of Vietnamese impeding English language literacy development.

Similarly, Ho-Dac (2003) did not find any evidence of a relation between the intense contact between Vietnamese and English and the decline of the Vietnamese language. In his study, code-switching was viewed as a strategy to overcome communication difficulties for Vietnamese immigrants living in Australia. In the same vein, Pham (2011) found that children in bilingual contexts can develop both languages, the heritage language, and the societal language at the same time (p. 68).

In the same vein, Maloof et al. (2006) selected 50 registered students at the Vietnamese Outreach Center in Atlanta, Georgia, which was developed to foster the maintenance of Vietnamese culture and language, and to promote biculturalism, to explore students’ integrated cultural identities. Participants ranged in age from 9 to 18 and had lived in the United States for at least two years. The research employed a questionnaire to access bicultural competencies and cultural identities as well as background data such as class participation, length of attendance and pattern of attendance. The findings showed a positive correlation between a strong cultural ethnic identity and the ethnic language proficiency as well as English language proficiency. Students who particularly have positive attitudes toward the ethnic culture tend to have especially positive attitudes toward the English language use. Therefore, it is undoubtedly true that positive feelings towards their home cultures enable students to more readily embrace the host country's language.

In the same vein, a study by Beth and Tuckermann (2008) in Germany argues that maintaining a heritage language is key to cultural preservation. The stories of participants provide evidence for this argument, as highlighted by Beth and Tuckermann (2008). One of the most fascinating stories involves a 20-year-old woman who strived to create a pleasant and supportive learning environment for her younger sister to maintain their heritage language. The older sister was motivated by her discomfort and distress seeing her sister's detachment from their culture, evidenced by her limited Vietnamese proficiency (about 10%) and having a German boyfriend). She believed that learning Vietnamese would remind her younger sister of her root (Beth & Tuckermann, 2008, p. 319). The older sister conveyed that Vietnamese language competence is an important part of retaining the heritage culture and should be maintained for future life and career prospects. She expressed, “Of course, in Germany, Vietnamese is not as necessary as German. However, I told her that it is our language. She can do it. It's in her essence. If she forgets or unlearns it, then someday she will not be able to do that anymore. And that is just too bad, because she never knows when she will need it again. She never knows if she might come back to Vietnam later. Not now, but to work or in a relationship” (ibid.).

In 2011, Lewis et al. designed two case studies on Vietnamese heritage language maintenance, the first being “The role of parent involvement in heritage language maintenance within a Vietnamese heritage language school setting”, the second being “Vietnamese American parents’ and students’ attitudes toward maintaining Vietnamese as a heritage language”. The findings from the above case studies showed that parent involvement and heritage language maintenance are key components for preserving cultural identity and for academic, and economic success.

In the same year, Lam (2011) examined the experiences of parents in mixed marriages (Vietnamese married to non-Vietnamese) regarding their efforts to maintain of the Vietnamese heritage language also in the United States. Although there were at least three different family types where language shift occured, parents were still trying to pass on the heritage language to their children.

Tran et al. (2021a) identified factors associated with language use of parents and attitudes towards Vietnamese heritage language maintenance through a survey. A analysis of 151 Vietnamese-Australian parents with children under 18 years old showed that parents’ language use with their children and in social situations strongly correlates with attitudes towards the heritage language of their children. The attitudes of parents towards the heritage language have strong influence on language ideology factors of children (the perceptions of cultural identity, the role of learning new language, and the potential resources for future career). The results of this study are consistent with existing research and argue strongly that Vietnamese heritage language maintenance is not a barrier to learn the language of host countries, but it is a potential resource for learning different languages and developing intercultural skills.

In summary, the current body of research consistently champions the preservation of the Vietnamese heritage language, highlighting its myriad benefits for individuals, immigrant communities, and host societies. Nonetheless, the bulk of these studies have been confined to the United States and Australia, underscoring the imperative for additional investigations in diverse host countries. This collective “voice” resounds with advocacy and endorsement for the safeguarding and nurturing of the Vietnamese heritage language within diasporic communities. It underscores the heritage language's intrinsic worth in fostering cultural identity, cultivating intercultural proficiencies, and bestowing overarching advantages upon individuals, immigrant groups, and host societies. The extensive evidence in existing research overwhelmingly supports heritage language maintenance and convincingly dispels any notion that it impedes the acquisition of the host country's languages. In essence, this resounding “voice” unambiguously promotes the preservation of the Vietnamese heritage language and fervently calls for further exploration of this pivotal subject.

Language Ideology and Language Practice

Attitudes towards the maintenance of the heritage language are strongly related to the language ideology and language practice. Tran (2006, 2013) paid attention to language practice of the Vietnamese diaspora community through the analysis of communication between family members in Vietnamese immigrant families in Nice, Paris and Lyon (10 registered families). Through the semi-structured interviews and participant observation, the study proposed a detailed picture of language practice of Vietnamese families in France: in order to overcome difficulties in Vietnamese communication at home, the children used various strategies, for example, generalization, approximation, borrowing, structuring, and code-switching.

König (2014) examined the language setting of bilingual Vietnamese-German adolescents during language biographical interviews to explore the linguistic construction of different “language spaces”, in which the participants positioned themselves as multilingual individuals. She found that the parents wanted their children to be proficient in both languages, Vietnamese and German; however, practicing German to adapt at German schools was more important (p. 298). In addition, she examined the motivation of the teenagers and young adults to maintain their heritage language. The case of Andrea showed that despite frequent use of the heritage language before going to school, she had to give up learning it because she did not have enough time (p. 304).

KiBis (Kinder auf dem Weg zur Bildungsprache) is another study in Germany that sought to describe the heritage language literacy practices of Vietnamese-German teenagers through qualitative analysis. As a case study, this research introduced the cases of Tai and Trang. In Tai’s case, he wrote Vietnamese without diacritics or tone marks and could not distinguish between tones such as thanh huyền (falling tone) and thanh sắc (rising tone). His writing style in Vietnamese mirrored his German writing (Gogolin et al., 2017, p. 42). Unlike Tai, Trang had to learn to write correctly in both German and Vietnamese. Her parents checked her spelling in both languages. In addition, she practiced dictation with Vietnamese children once per week and therefore, she could write quite well in Vietnamese.

Particularly, Tran (2021b) describes the family language policy of the Vietnamese community in Australia. The analysis reveals that a third of the participants (35.6%) had a family language policy and 72.5% of those consistently implemented it. Significantly, the parents in families with a family language policy obtained higher Vietnamese proficiency, used Vietnamese more frequently with their children and often intended to come back to Vietnam.

In examining the intricate interplay between heritage language attitudes, language ideology, and language practice within the Vietnamese diaspora, a resounding voice emerges. It underscores the dynamic nature of heritage language maintenance and the complexities faced by individuals and families navigating this linguistic journey.

This voice emanates from Tran's (2006, 2013) meticulous investigation of Vietnamese immigrant families in France, revealing the ingenious strategies employed by children to overcome communication barriers within their own homes. It resonates in König's (2014) exploration of bilingual Vietnamese-German adolescents, where the aspiration for proficiency in both Vietnamese and German clashes with the practical demands of academic success in Germany. It is also evident in KiBis study's (Gogolin et al., 2017) depiction of Tai and Trang, two contrasting cases that illuminate the challenges and successes in heritage language literacy. Moreover, this voice finds resonance in Tran's (2021b) description of family language policies within the Australian Vietnamese community, where a commitment to such policies correlates with enhanced Vietnamese proficiency and a profound connection to Vietnamese culture. Throughout these narratives, the voice is one of resilience, adaptability, and the enduring significance of heritage language in the face of evolving sociolinguistic landscapes. It calls for continued exploration, recognizing that the intricate relationship between attitudes, ideology, and practice holds the key to preserving the Vietnamese heritage language within diasporic communities worldwide.

Vietnamese Heritage Language Education and Policy

Heritage language schools or programs of heritage language education have also received attention from researchers. The language use and cultural programs have been examined in terms of their quality. Maloof et al. (2006) stated that heritage language and cultural programs can promote the advantage of maintaining heritage languages. However, the Vietnamese heritage language programs in the United States still faced many difficulties as follows:

(1) a broad, uneven range of instructors’ skills levels and pedagogical training, (2) a diversity of students’ skill levels and immigration patterns, (3) a lack of cultural sensitivity to diasporic acculturation issues regarding homeland politics, (4) the U.S. national neglect of embedded regional politics that play out in the classroom, (5) the possible geopolitical slant of resource and instructional materials, (6) U.S. federal and local funding systems, and (7) academic institutional infrastructural problems that affect interest in language study.

(Lam, 2006, p. 2).

Tran (2008) introduced Vietnamese language education in the United States in language schools and teaching programs at some institutions, such as the Vietnamese literacy training program of the Parker Williams Branch Library in Harris County in Texas, and teaching courses at some universities. These programs were organized through the efforts of professors and teaching staff with Vietnamese migrant backgrounds. Due to limited funding, these schools usually lacked well-trained teachers and teaching materials (ibid., p. 264). These issues were mitigated by the development of new materials, especially language software, cultural software and media. However, there were still a lot of challenges in teaching the Vietnamese heritage language. One of the challenges was the attitudes of the learners. Nguyen (2016) informed that some heritage learners felt uncomfortable learning Vietnamese because they did not self-identify as Vietnamese. Another difficulty arised from the feelings of heritage speakers about dialect accents. For example, Jane, who grew up in a family from Central Vietnam, was accustomed to the Hue accent. She found the Northern accent “foreign” and “strange” (ibid., p. 44). In addition, her classmates mostly spoke with the Southern accent. She felt more comfortable with the Southern accent than the Northern one. Therefore, she tried to learn this accent to avoid becoming “an oddball” (ibid., p. 44). The problems of heritage learners can bring difficulties for heritage language teaching.

Surprisingly, there have been a few studies regarding Vietnamese heritage language education and policy. This topic deserves greater attention due to the necessity of creating suitable language and cultural programs in different Vietnamese communities around the world.

The voice embedded within this passage is one of recognition and concern for the challenges faced by Vietnamese heritage language education and policy in the United States. It echoes the sentiments of researchers like Maloof et al. (2006) and Tran (2008), who shed light on the numerous obstacles impeding the success of heritage language programs.

This voice articulates the issues surrounding these programs, encompassing instructor skills, diverse student backgrounds, cultural sensitivity, political dynamics, funding, and academic infrastructure. It speaks to the persistent struggle for adequate resources and well-trained educators in Vietnamese heritage language education.

Furthermore, this voice resonates in the portrayal of difficulties faced by learners, including discomfort stemming from self-identity issues or regional dialect variations. It underscores the intricate web of factors influencing the effectiveness of heritage language teaching.

Overall, the voice conveys the urgent need for increased attention, resources, and tailored language and cultural programs within Vietnamese communities worldwide. It underscores the significance of addressing these challenges to ensure the preservation and revitalization of the Vietnamese heritage language.

Vietnamese Heritage Language Proficiency Assessment

The language proficiency of heritage speakers has been investigated in early research related to the Vietnamese heritage language. The study of Nguyễn et al. (2001) involving 588 participants with self-reports, surveyed individuals regarding their competence in the Vietnamese language. The majority, 60% of the participants, reported that Vietnamese was their first language, while 7% indicated English as their primary language, and 26% claimed proficiency in both languages. Additionally, 8% of respondents were unsure about their first language. Concerning speaking abilities, 67% of the participants stated that they spoke Vietnamese very well or well, while 25% felt their Vietnamese proficiency was okay, and 7% had limited or no speaking skills in Vietnamese. When it came to reading and writing, 23% reported being proficient, 19% felt they were okay, and a significant 58% had little or no ability in reading and writing Vietnamese (Nguyễn et al., 2001, p. 162).

The results showed that the majority of participants thought Vietnamese was their first language. Through self-evaluation, speaking competence was good, but their literacy competence was still poor.

In the same topic, Maloof et al. (2006) measured Vietnamese heritage language proficiency by self-reports in two domains: communication and cultural content. The communicative domain was accessed by self-reported competence in four skills: understanding, speaking, reading, and writing with nine-interval Likert scales (1 = not at all, 9 = very well). The cultural content was identified by inquiring into some cultural language aspects such as proverbs and ethnic holidays. Additionally, the cognitive competence was evaluated through reports about four student skills (understanding, speaking, reading, and writing) that were conducted by language center teachers. Of the 33 test students, 12 were identified as low in Vietnamese heritage language proficiency.

Bui (2016) shed light on Vietnamese heritage language competence among adolescents. To investigate language interest, she conducted surveys with Vietnamese immigrant teens in the United States (n=22, aged 14-35) and Germany (n=21, aged 13-29). In the US, 50% of participants reported good speaking and listening skills, but only 14% could read and write Vietnamese well (p. 146). Notably, in Germany, 50% of participants demonstrated proficiency in all four language skills, particularly reading and writing. This higher proficiency is likely due to parental expectations and frequent Vietnamese language use at home (ibid., p. 230).

In terms of language competence of Vietnamese-German adolescents, Hegele (2014) found that most migrant children could speak German almost fluently, whereas their parents often had problems with this language. The participants of this study could speak Vietnamese well, but they had difficulties in literacy because they had not learned Vietnamese at school (p. 11). This is a story of a participant:

I can understand all, it is sometimes for me difficult with vocabulary, and then I must sometimes ruminate. Actually, I can talk quite well, but writing and reading are hard for me… I learnt this at home, we speak Vietnamese. That’s why I also have problems in reading and writing, because I did not learn it in a school. However, I firstly learnt Vietnamese, therefore it is my mother tongue. (Hegele, 2014, p. 11)

Tran (2018, 2019) described Vietnamese heritage language performance through writing skill of Vietnamese-German adolescents to explore to what extent these heritage speakers could write Vietnamese. A quantitative evaluation form was developed to measure the written texts of 20 participants across two different time points. This form was evaluated to determine whether it was reliable for application in other studies. In addition, in order to describe in more detail the written language performance of this target group, a qualitative analysis of collected written and translated texts of Vietnamese bilinguals and monolinguals was carried out. The results showed that 3 out of the 12 evaluation categories were required further consideration. The qualitative analysis provided a comprehensive description of Vietnamese heritage language characteristics in the written performance of Vietnamese-German adolescents that will be described in the next section.

The voice underlying the existing studies is one of commitment to understanding and assessing the language proficiency of Vietnamese heritage speakers. It reflects the dedication of researchers to uncover the intricacies of language competence among heritage speakers, particularly those of Vietnamese descent living in different countries.

The existing research has typically  used self-reports and various evaluation methods to measure Vietnamese heritage language proficiency. These studies seek to gauge competence in speaking, reading, writing, and understanding Vietnamese. However, there is still a lack of comprehensive data collection. The voice within the passage emphasizes the importance of such research to provide a holistic view of heritage language competence.

Additionally, it underscores the variation in language proficiency among Vietnamese heritage speakers in different contexts. Some individuals demonstrate proficiency in speaking but struggle with literacy, while others excel in all language skills due to cultural expectations and practice at home.

Moreover, the passage's voice also advocates for the development of objective evaluation methods, combining quantitative and qualitative assessments to comprehensively measure Vietnamese heritage language proficiency. The aim is to provide educators, linguists, and teachers with valuable insights to design effective language programs.

Overall, the voice of these studies promotes a deeper understanding of Vietnamese heritage language proficiency, advocating for comprehensive assessment methods and further research in this area to benefit both learners and educators.

Characteristics of Vietnamese Heritage Language

Studies on characteristics of Vietnamese heritage language are briefly summarized in Table 7.2.

Table 7.2 Summary of published studies on Vietnamese heritage language characteristics

Most of the above studies were based on oral data; only two studies by Tran (2018, 2019) analyzed written data. The informants of existing research are adolescents and adults. There are still a lack of studies about the taxonomy of Vietnamese heritage language among young children.

The most prominent feature that appeared frequently in language use through generations and in all data is code-switching and transfer. Ho-Dac (2003) analyzed code-switching in syntax, tonal facilitation, and personal pronouns of Vietnamese-English bilinguals in Melbourne, Australia through face-to-face interviews and 11 natural conversations.

Firstly, the frequency of code-switching by word classes was discussed. The proportion of English nouns that excluded proper nouns was more than 50 percent of the total switches. The switched nouns were distributed among some of the following semantic categories such as accommodation (flat, bedroom, motel), landscape (city, park, tram), work-related (team, office, boss), food (milk, cereal, dinner); institution (tax, court, police), household (furniture, kitchen, cook), shopping (shopping center, sale, op-shop), education (Math, library, exam), and Australian way of living (cricket, pub, safari).

Secondly, the relationship between code-switching patterns and topics was examined. The results showed that code-switching happened frequently in some conversation topics about books and films (21.51%), daily work in Australia (16.22%), and the Australian culture (12.04%) (ibid., p. 73).

Finally, code-switching in personal pronouns was considered a strategy to handle identities. Specifically, the switch of a Vietnamese address form to an English personal pronoun signaled the attitude change of the speakers. For example, Vietnamese pronouns mày – tao as informal address forms appeared dominantly to show the close and intimate relationship between friends. One speaker changed address forms to the English pronoun me to create distance between herself and her friend.

To sum up, Ho-Dac (2003) considered code-switching as a critical feature of the Vietnamese language variety of heritage speakers living in Australia. Code-switching was seen as a strategy to make conversations in Vietnamese in an English environment. At the grammatical level, code-switching of content words such as nouns, verbs, and adjectives occurred more frequently than with function words. However, the usage of English words was influenced by the rules of using the Vietnamese grammatical structure, such as the lack of word change in all positions within a sentence. In addition, the code-switching of address forms could express the change of speakers’ attitudes which are traditionally implied in the Vietnamese language and culture.

Another study on code-switching and transfer as prominent characteristics of bilingual conversation is Thai (2007). In this study, he examined the relationship between code-choice, code-mixing and identities. Thai (2007) recorded 53 conversations, in which there were 28 participants aged 22–62 living in Australia for at least 5 years (Pritchard, Springvale, and Belconnen). Participant worked in many different jobs ranging from doctors, IT engineers, writers, students to housewives. 12 of the participants were fluent Vietnamese-English bilinguals.

Interestingly, based on the collected data, he proposed the forms of lexical renewal, such as the creation of new words that was based on English lexical vocabulary: đi làm pham (go make farm—seasonal fruit picking), tách phom (separate form–separated couples), làm neo (make nail—manicurist). In the existing examples, English words farm, form and nail were not only Vietnamized at the phonetic and graphic aspects, their meanings were also mostly broadened. Particularly, in the standard Vietnamese, đi làm ruộng (working on the farm) is manual planting, waterring and harvesting, whereas đi làm farm in the Vietnamese heritage language variety in Australia refers to seasonal fruit-picking or sometimes as cash-paid seasonal labor. Semantic expansion occurred frequently because of the impact of English homonyms or the preference of archaism in the migrant language (Clyne, 1985).

Tran (2006, 2013) also described Vietnamese heritage language through daily conversations in Vietnamese immigrant families in France, particularly in Nice, Lyon, and Paris. Her studies argued that address forms in communication between different generation were influenced by French language and culture in both horizontal and vertical relationships. Frequency of using the pair address mày-tao (moi-tu in French, you-I in English) and the limited knowledge of pronouns were considered two features of Vietnamese heritage language in France.

Dao (2016) attempted to define characteristics of English loanwords in the Vietnamese lexis of the Vietnamese-Australian immigrants. The study showed that nouns obtained the highest proportion of English loanwords in the Vietnamese vocabulary of Vietnamese-Australian immigrants, about 87.6% (p. 209). The semantic fields of English loanwords were from a wide range of places. The semantic fields of health, business and economy, cars/vehicles/aviation, housing, and dwelling obtained the highest proportions, respectively about 8.8%, 8.1%, 7.7%, and 7,6% (ibid., p. 210).

Interestingly, in Dao’s study (2016), the orthography of English loanwords was based on the Vietnamese orthographic system with tones, diacritics and/or hyphens between syllables, for example, ơ-cao for account, chạc for charge. Many words were borrowed in order to “designate new things, persons, places, and concepts” (Weinreich, 1974, p. 56). However, Vietnamese-Australian immigrants used English words for many things that already had their own names in the Vietnamese language such as casino for sòng bạc, seat belt for dây an toàn. It was evidence of the high level of “penetration of English loanwords in the Vietnamese language in Australia” (ibid., p. 213). In addition, about 39.1% of loanwords are loan translations. For example, pension age is translated to tiền già (lit. old money).

Dao (2012, 2017) and Dao and Nguyen (2015) also described transfer and code-switching with regard to the phonetic aspect. Through phonetic tests and language background questionnaires, the study showed the divergence of production of the tones and vowels between the young Vietnamese residents in Australia and the older Vietnamese residents in Australia (p. ii). Specifically, young Vietnamese Australians were unable to produce the broken-curve tone of Southern Vietnamese dialect. Tones in the same register of similar characteristics such as the level and rising tone and tone diacritics such as the falling and the rising tone were confused. The vowel productions of young Vietnamese-Australians were also distinct from those of  older Vietnamese-Australians and native speakers, due to the influence of the transference of English. Despite the existence of the close mid /e/ in Australian English, young bilinguals tended to produce the English vowel /e/ instead of the Vietnamese vowel /ε/. It was explained by the difficulty of distinguishing between /ε/ and /e/ in the Vietnamese language. These two vowels are described as front, mid, unrounded, but /ε/ is pronounced more open than /e/ (Dao & Nguyen, 2015, p. 302). In addition, the similarity of e and ê, o and ô is also brought difficulty for the participants when they had to read the test.

Phan (2017, 2018) focused on the linguistic characteristics of the Vietnamese language in the United States. Twenty-four illustrated frames of a wordless children's story were used as a test instrument to collect participants’ oral data. Consistent with findings from  Ho-Dac (2003), Tran (2006, 2013), Thai (2007), Dao (2016), code-switching appeared frequently in the Vietnamese speech of Vietnamese-American participants. These loanwords were predominantly used within Vietnamese syntactic frames, regardless of participants' varied levels of Vietnamese fluency. This finding supports Montrul’s (2012) argument about “the most resilient areas” (p. 20), which are passively acquireded through consistent heritage language exposure within family settings (Phan, 2018, p. 8).

Code-switching has also been investigated in Tran (2018, 2019). This aspect was measured by self-reports with a 4-point scale of the frequency level of code-switching in the conversation between Vietnamese-German adolescents with different people. The results showed that code-switching often appeared in communication between children and their mother/father, whereas it happened only between certain people in communication between heritage speakers with siblings, and best friends. It never or rarely occurred in conversation with classmates, neighbors, and friends. Specifically, Tran’s studies focused on lexical code-switching and transfer. The results were consistent with existing studies by Ho-Dac (2003) and Thai (2007) in written and translated texts of Vietnamese-German adolescents: (1) High frequency of code-switching from German to Vietnamese; (2) Existing code-switching from English; (3) More frequency of code-switching in content words (verb and noun); (4) Use of infinitival form of words in code-switching (fliegen (fly) instead of fliegt, smooth down instead of smooths down); (5) monosyllabization of borrowed words (bau instead of bauen (build)); (6) Use of basic or general words for specific words in loan translation and semantic extension (làm—make instead of paint, saw, sew).

Several studies highlighted the fossilization of vocabulary among first-generation heritage speakers. Interestingly, Ho-Dac’s study revealed that certain words such as thủ lãnh (leader), nhật trình (daily newspaper), or proper names of many countries as Hoa Lục (China), Hoa Thịnh Đốn (Washington), Úc Kim (Australian Dollar) have no longer used in Vietnam since 1975, but persisted in the spoken and written language of Vietnamese immigrants in Australia. New Vietnamese vocabulary has replaced these terms within Vietnam, for example, lãnh đạo for thủ lãnh, Trung Quốc for Hoa Lục, Washington for Hoa Thịnh Đốn, Đô la Úc for Úc Kim. Another feature of lexical use in the Vietnamese heritage language variety in Australia was the scarcity of new vocabulary adopted after 1975 such as bao cấp (budget subsidies), hộ khẩu (number of inhabitants), quần chúng (the masses). The issue of fossilization of language routine and the lack of new vocabulary among immigrant communities can likely be attributed to limited contact with their native language in their home countries. Thai (2007) additionally discussed the frequent use of the passive voice, the adoption of address forms you and me, and the common use of expressions like thank you and sorry.

Dao (2016) compareded monolingual Vietnamese newspapers published in Australia such as Việt Luận (Vietnamese Herald), Chiêu Dương (the Sunrise), and Nhân Quyền (Human Rights) with those published in Vietnam such as Tuổi Trẻ (the Youth), Thanh Niên Newspaper (the Youth Newspaper), and Tin nhanh Việt Nam (Express News of Vietnam). The analysis revealed a high frequency (79%) of obsolete vocabulary use in the Australian Vietnamese newspapers. The proportion of obsolete nouns were higher than obsolete verbs (13.8%) and adjectives (5.7%). Notably, vocabulary related  to political institutions such as government, politics and legal matters were preserved in these publications. Furthermore, 18.3% of the obsolete vocabulary stemmed from older South Vietnamese dialects, with spellings reflecting southern pronunciations, for example, chánh phủ (goverment) instead of chính phủ, cá nhơn (individual) instead of cá nhân. Finally, the study found  60.5% of the obsolete vocabulary used in Vietnamese newspapers in Australia consisted of Sino-Vietnamese terms, most of which  have no longer used in contemporary Vietnamese, such as chiếu khán (visa) for thị thực, Lã Phụng Tiên (La Fontaine) for La Fontaine.

Other several features have been described in studies by Phan (2017, 2018) and Tran (2018, 2019). Although there aren't many other studies in the same area, the findings of these studies are interesting and meaningful for research on Vietnamese heritage language. Their studies examined the use of classifiers, the use of the indefinite determiner một, the use of the indexical cái within noun phrases, the use of đã/rồi, đang, and the use of causative constructions. In Phan's works (2017, 2018), classifier use included errors such as omissions, misuse, and overuse that varied among participants another. Classifier con was mostly used correctly due to its distinct meaning of [+animate]. In constrast, the general classifier cái (Tran, 2011) was often misused in place of more specific classifiers. Additionally, (Tran, 2011) found the overuse of the indefinite determiner một and the indexical cái (not CL cái, that is extra cái). The wrong use of the indefinite determiner một might result from the influence of the indefinite article a/an English. Heritage speakers used the indexical cái significantly more than native speakers, though the author did not provide a detailed explanation for this finding in details.

Expanding on this topic, Tran (2019) demonstrated that classifier omission was the most common classifier-related issue in Vietnamese heritage language, likely influenced by the absence of classifiers in German. Consistent with the findings of Phan (2017, 2018) and Tran (2011), the classifiers con, cái and chiếc were the most frequently used, reflecting their prevalence in the Vietnamese monolingual environment.

Shifting the focus to defining characteristics of the Vietnamese heritage language in Germany, Tran (2018) examined the verb use of Vietnamese-German adolescents. A nine-picture set of building a boomerang was used as the instrument to collect written data of 25 participants. A separate translation test  (from English) involved text was used for a translation test involved 20 different participants. The results indicated a tendency or a strategy towards simplification in verb use, where basic verbs like làm (make), nhìn (see), or nói (talk) were used frequently over more specific verbs. Tran's 2019 dissertation expands on this research, offering a more comprehensive analysis of the Vietnamese heritage language among adolescents in Germany.

In addition, Tran’s dissertation (2019) also identified the common characteristics within the Vietnamese heritage language across various linguistic levels, as demonstrated in both the boomerang written texts and the translated texts. At the orthographic level, these features included deletion of diacritics, word initial capitalization, grapheme replacement due to transfer from German orthographic rules (e.g., <k> instead of <c>, <n>, <ng> instead of <nh>), grapheme confusion due to interlanguage resources (e.g., <s> and <x>, <i> and <y>), reduction of digraphs and trigraphs (e.g., <ư> instead of <ươ>, <n> instead of <ngh>). At the lexical level, the study revealed a smaller vocabulary size in Vietnamese-German adolescents compared to their monolingual peers. This was evident through the analysis of total words, compound words, and Sino-Vietnamese words, which were used by participants. At the pragmatic level, Tran's work specifically focused on the complex and context-dependent Vietnamese address form system. Results indicated that  Vietnamese-German adolescents favored to use the intimate informal address forms such as the pronoun mình (used to address and refer in intimate relationships), and kinship terms em, con, cháu instead of formal address forms such as tôi, chúng tôi in the formal contexts provided by the written and translated tasks. The findings suggested that the adolescents' written productions of the Vietnamese-German adolescents reflect strategies like “write the way they speak” (Chevalier 2004); and “simply writing down everything” (Danzak 2011: 501).

The voice embedded in these studies is one of thorough examination and documentation of the linguistic characteristics and behaviors found within Vietnamese heritage language communities around the world. These studies demonstrate a deep commitment to unraveling the complexities of language use, evolution, and maintenance among Vietnamese diaspora communities.

Firstly, the voice in these studies emphasizes the significance of code-switching and transfer as prominent features within Vietnamese heritage language communities. It delves into the reasons behind code-switching, whether it's a strategy for communication in other host language-speaking environments, a reflection of identity shifts, or a way to navigate complex social relationships. The studies illustrate how code-switching is not merely a linguistic phenomenon but is deeply intertwined with cultural, social, and psychological aspects.

Secondly, the voice stresses the persistence of obsolete vocabulary and fossilization of language routine within these communities. This highlights the importance of examining not only how languages evolve but also the processes through which they can become fossilized or undergo selective change based on the context of migration and cultural contact.

Moreover, the voice is dedicated to studying the influence of English and other language loanwords and the adaptability of Vietnamese in response to the linguistic environment of the diaspora. It explores the creative lexical renewal processes and demonstrates how loanwords can reshape and broaden the meaning of existing vocabulary.

Furthermore, the voice shows concern for the younger generations of Vietnamese heritage speakers, discussing language proficiency, phonetic variations, and grammatical features among adolescents and children growing up in diaspora communities. These studies provide insights into how these young speakers navigate linguistic complexities, often influenced by their bilingual upbringing.

The voice across these studies is characterized by a strong commitment to understanding the dynamics of language use and change within Vietnamese heritage language communities. It emphasizes the need for in-depth linguistic analysis to shed light on the intricate relationship between language, identity, and cultural adaptation among Vietnamese diaspora populations.

Conclusion

The voice of Vietnamese heritage language research has transitioned from silence to empowerment, offering a newfound voice to Vietnamese heritage speakers who have been overlooked. Heritage speakers “who are used to being silent in their first language a new voice, one that can make them truly bilingual and bicultural” (Boom & Polinsky, 2014, p. 17). This transformation fosters an embrace of bilingualism and biculturalism. Nevertheless, the voice of Vietnamese heritage speakers requires further exploration from diverse perspectives, as research on this matter still exhibits considerable gaps, encompassing both entirely novel topics and unexplored facets of existing subjects.

The issue of Vietnamese heritage language loss, shift, and maintenance has garnered substantial attention in the United States and Australia. However, there remains a pressing need to examine these phenomena across a wider spectrum of age groups, various communities, and an array of related variables. Despite some progress in researching Vietnamese heritage language education and policy, there's still much more to explore in this field. To formulate effective language and cultural programs that cater to Vietnamese heritage language speakers worldwide, comprehensive research in this domain is imperative.

Evaluating the proficiency of Vietnamese heritage language has largely relied on self-assessment, which often lacks precision. Therefore, the development of comprehensive evaluation criteria for Vietnamese heritage language proficiency becomes essential. While the study of Vietnamese heritage language characteristics has expanded in recent years, there is still a demand for advanced perspectives explored in diverse settings and using varied data sources. Notably, exploring Vietnamese heritage language from a cognitive perspective remains an uncharted territory. Furthermore, pedagogical approaches to teaching Vietnamese heritage language sometimes overlap with teaching Vietnamese as a second language. Lessons from comprehensive studies on Spanish heritage language education can provide valuable insights and methodologies for researchers in the Vietnamese heritage language domain.

In summary, the call for extensive research on Vietnamese heritage language, spanning multiple dimensions, is not only to elevate its status “from the margins to become a central focus” (Montrul, 2016, p. 6), akin to certain other heritage languages, but also to amplify the voices of Vietnamese heritage speakers within society.