The present study was triggered by the inconsistency in verbal descriptors in English and Korean describing ‘warm’ and ‘hot’ in the thermal sensation scale. The purpose of this study was to examine the linguistic dimensions of the terms expressing ‘ttatteuhada (warm)’ and ‘yakkan duptta (slightly hot)’ in Korean. A total of 988 urban Koreans (479 males and 509 females) participated in a questionnaire survey consisting of six questions. The one-to-one survey was conducted indoors in December 2008. Our results showed that (1) ‘warm’ and ‘slightly hot’ in Korean are distinctive thermal descriptors; (2) ‘warm’ projects thermal comfort (80.4% of 988 respondents), but ‘slightly hot’ projects some thermal discomfort (54.3% of 988 respondents); (3) a slight thermally comfortable feeling was expressed as ‘warm’ (83.9% of 988 respondents), while a slight thermally uncomfortable feeling was seldom expressed as ‘warm’ (6.2% of 988 respondents) in mild heat environments; (4) the linguistic dimension within the term ‘warm’ was less affected by individual thermal susceptibility (vulnerability) than that of the term ‘slightly hot’. In summary, ‘warm’ in Korean connotes a thermally comfortable feeling. In the case of being a little thermally uncomfortable, Koreans project their thermal sensation through the term ‘slightly hot’, rather than ‘warm’. In conclusion, thermal descriptors in the ISO 10551/ASHRAE scale, i.e., ‘very cold–cold–cool–slightly cool–neutral–slightly warm–warm–hot–very hot’, are not valid for the evaluation of mild hot environments in Korea. A new categorical scale is required in Korean considering the descriptors ‘warm’ and ‘slightly hot’.