Avoiding Ambiguity

  • Michael Alley


The disastrous charge of the Light Brigade at Balaclava in the Crimean War was made because of a carelessly worded order to ‘charge for the guns’—meaning that some British guns which were in an exposed position should be hauled out of reach of the enemy, not that the Russian batteries should be charged.

An ambiguity is a word, phrase, or sentence that readers can interpret in more than one way. In poetry, readers celebrate ambiguity. For instance, critics delight in the ambiguity of the last two lines of a poem by e. e. cummings about Buffalo Bill Cody [2]:

How do you like your blue-eyed boy

Mister Death

Is the poem a eulogy to a western hero or a condemnation of all the animals that he killed? In other words, does “Mister Death” at the end of the poem refer to a spirit or to Buffalo Bill himself? Because of the lack of punctuation, these last two lines can be read in two distinct ways. Like poetry, art also finds delight in ambiguity, such as in the Escher-like facade of Figure 3-1 [3]. Here, the ambiguity lies in whether the lizards are gold or white.
Figure 3-1

Ambiguity in a building’s façade, which follows a design by Escher. Are the lizards gold or white?

Although ambiguity is cause for celebration in poetry and art, ambiguity frustrates a scientific reader: Open image in new window

Does the solar collector work at a height that is well below the passing clouds, or under passing clouds, does the solar collector work well? Such an ambiguity leads audiences to waste time by having to reread a passage to discern the correct meaning. Other ambiguities, particularly in instructions, can lead readers to make errors, which in technical instructions can lead to failure of a structure or injury to a person. While poets and artists garner praise for ambiguities, engineers and scientists receive lawsuits.

So how do you avoid ambiguities in scientific writing? Before addressing that question, let us consider the following excerpt from a report submitted by an engineer: Open image in new window

Three ambiguities riddle this description. First, are the general requirements for the radiometer system or something else? Second, in the first requirement, who or what must survive? A third ambiguity concerns the number of requirements, because the first requirement has two criteria. In this excerpt, haste on the author’s part most likely led to these ambiguities. Attention to precision and clarity gives the following revision: Open image in new window

Ambiguities are difficult to catch on first drafts when your focus is on placing complex ideas onto paper. Rather, the best time to catch ambiguities is during the revision stage when you can view the writing as your readers will.

Some engineers and scientists lament about how tired they are after writing a first draft. “I cannot look at it anymore,” they say. “It is too painful.” Perhaps the writing is painful, especially if it was drafted with the same lack of clarity as in the radiometer example above. However, the writing represents your work, and if you spent significant time and effort doing the work, then you should also spend a reasonable amount of time and effort documenting the work. Attaining clarity does not occur on first drafts when you have a blank computer screen staring at you. Rather, you attain clarity on later drafts when you have your ideas, calculations, and measurements in front of you. Although the ambiguities in the radiometer example are difficult to classify, many ambiguities arise from four specific sources: word choice, word order, pronouns, and punctuation.

Avoid words with multiple interpretations

Many words in English have multiple meanings. For instance, the word right has a meaning referring to “correctness” and another meaning referring to “direction.” In most instances, the intended meaning of such words are clear. However, in scientific writing, situations arise in which using such words leads to multiple interpretations: Open image in new window

Does the word as mean “while” or does it mean “because”? A reader could easily interpret the word either way. In scientific writing, having the meaning teeter in two ways is unacceptable. In this example, the engineer wanted the meaning “because.” For that reason, the engineer should choose the word because, which has only one meaning.

In other types of writing such as poetry, using the word as to mean “because” would be not only allowed but also encouraged. Because syllable count in poetry is important, opting for the one-syllable word as can be justified. However, as Lesson 2 discussed, professional readers see both one-syllable words and two-syllable words as short words [4]. For that reason, when you want the meaning of “because,” you should select the word because: Open image in new window

Consider the ordering of words, especially the word only

When scientists and engineers are not careful about the ordering of words and phrases, ambiguities can occur: Open image in new window

This sentence contains an ambiguity: Does the schedule extend for 4 years or will the discussion of the schedule take the reader 4 years to read? As you might expect, the writer intended the first meaning. Although readers upon reflection would arrive at the first meaning, they would have wasted time thinking about this tangential question. The source of this ambiguity is the positioning of the prepositional phrase “for the next four years.” This detail about time occurs too late in the sentence. Revision gives— Open image in new window

Unlike most languages, the English language is flexible in terms of word order. For instance, from the perspectives of grammar and clarity, you may write any one of the following:

We located the satellite.

The satellite was located by us.

The satellite we located.

Which order you choose would depend on the desired emphasis and the transition from the previous sentence.

In German, because precision is such an important part of the culture, such flexibility does not exist. In fact, the German language even has a specific order for modifiers: (1) details about time, (2) details about manner, and (3) details about place. Time, manner, and place—such an order avoids many ambiguities that arise in English. When confronted with the insertion of several details in a sentence, you would do well to remember the German sequence.

The improper placement of phrases, particularly introductory phrases, can also cause ambiguities. Open image in new window

Let us hope that the technician conducting the tests survived as well. Revision with attention to clarity gives Open image in new window

One word in English probably causes more ambiguities because of its placement than any other. This word is only:

Only I sighted the cheetah yesterday.

I only sighted the cheetah yesterday.

I sighted only the cheetah yesterday.

I sighted the only cheetah yesterday.

I sighted the cheetah only yesterday.

This example presents five different arrangements of this six-word sentence, and each sentence has a different meaning. The word only often causes problems because the word is sometimes an adjective (first and fourth sentences) and sometimes an adverb (second, third, and fifth sentences). Be careful about the placement of only. When you see it during a revision, a red flag should go up telling you to make sure that the word occurs in the proper position.

Be selective with it and avoid the standalone this

According to Fowler’s A Dictionary of Modern English Usage , which is a bible of sorts for the use of words in English, the reader should not have “even a momentary doubt” as to what a pronoun refers [5]. Many scientists and engineers, unfortunately, do not abide by this principle: Open image in new window

What is mounted in the container? The receiver? The radiometer? The environment? The noun environment is the nearest possible reference to the pronoun it, but that reference makes no sense. The noun receiver receives the most emphasis in the sentence but three pages later in this report, the reader learns that the receiver stands more than 15 meters tall, making it much too large to fit into the container. In other words, the engineer had intended the pronoun it to refer to the noun radiometer, although this noun was neither the noun nearest to the pronoun nor the noun that received the most emphasis in the sentence. Given the number of possible references in this example, the engineer should have just repeated the noun radiometer. Open image in new window

The way that many scientists and engineers treat the pronoun it is unsettling but the way that many scientists and engineers treat the word this is criminal: Open image in new window

What does the chemist want the word this to refer to? To the last noun of the previous sentence: oil? To the subject of the last sentence: concentration? To the idea of the previous sentence: that no significant concentration of olefinic hydrocarbons exists? Actually, the word this in this example refers to none of these. The chemist intended the word this to refer to the lack of peaks in the olefinic region.

Unlike it, which is a pronoun and nothing else, the word this is a special type of adjective, which journalists occasionally use as a pronoun to refer to the idea of the previous sentence. Unfortunately, many scientists use the standalone this much more often. Worse yet, many of those uses refer to different things: the last noun used, the subject of the previous sentence, the idea of the previous sentence, or something else. Instead of using this as a pronoun, clarify your writing by letting this do what it does best—point. Open image in new window

While inserting the standalone this is relatively easy for the writer, interpreting the standalone this can be much work for the audience. Much as a tired basketball player will lean and grab hold of her or his shorts during a free throw, using the standalone this is a sign that the author has become tired. The result can cause confusion, as occurred in the following email: Open image in new window

What did the email’s author want the audience to forward? The pronoun placement indicates that the writer wanted the audience to forward the virus “to as many people as you can.” However, logic dictates that the author wanted the audience to forward the warning, not the virus. Therefore, the author should clarify that meaning: Open image in new window

Although the revision required the author to spend an additional word, the expenditure was worthwhile because the audience could now gather the intended meaning on the first reading.

Insert commas after introductory phrases and clauses

A fourth common source of ambiguities arises from missing punctuation. As Bernstein writes, punctuation marks act as road signs in the writing.6 These marks tell readers when to stop and when to slow down. Especially important for preventing ambiguities are commas. Commas act as yield signs that tell readers when to slow down so that they will see the sentence in a certain way.

Many rules exist for commas. While some rules are not mandatory, others are. In scientific writing, when a comma is needed to keep a sentence from being misread, the comma is mandatory. Consider an example in which someone did not follow this rule: Open image in new window

This sentence requires a comma after “cooling.” Otherwise, readers do not know where the initial phrase stops and the main part of the sentence begins. Consider another example: Open image in new window

Here, the engineer needs a comma after “off.”

When defending their decision not to include a comma after an introductory phrase or clause, some engineers and scientists refer to a mysterious rule about the number of introductory words before a comma can be used. No such rule exists. For instance, if you begin a sentence with the word however to mean “on the other hand,” that word must be followed by a comma—no exceptions. Otherwise, the audience could assume that however has the meaning of “no matter how.” The bottom line is that if you are in doubt about whether to insert a comma after an introductory phrase, then do so. After all, it is not incorrect to have a comma after an introductory phrase or clause, even when the comma is unnecessary.

In addition to the absence of commas after introductory phrases, a source of ambiguity involves missing commas in a series of three or more items. In such a series, the guideline for engineers and scientists in the United States is that commas should separate each term:

The three elements were hydrogen, oxygen, and nitrogen.

Engineers and scientists in other parts of the world do not follow this guideline. Instead, their guideline is to drop the comma after “oxygen” unless not having the comma causes ambiguity. However, lists in science and engineering commonly arise in which not having a comma does cause an ambiguity: Open image in new window

In this sentence, no matter whether you work in Dallas or Dublin, you should place a comma after “circuits.” Otherwise, your readers will waste time deciphering the meaning: Open image in new window

Punctuating lists in scientific writing requires special attention, because lists in science and engineering can be complex. Consider the following sentence from a recent journal article: Open image in new window

A question arises: How many fuels did the chemist examine? Four? Three? Two? One? A good lawyer could make a case for any of the four answers. In this particular example, a table in a later section of the paper revealed that the chemist had examined four fuels. To rid the above example of the ambiguity, the chemist would have benefitted from a colon and a return to the United States guideline for punctuating items in a series: Open image in new window

More important than which guideline you choose for punctuating a series of items is that you check to make sure that the audience can read the list only one way.

As stated, ambiguities are difficult to find when you first draft a document. Just after a drafting session, the sentences are no longer fresh. What you need is distance from the draft. A good night’s sleep provides such distance. Also providing distance is a different look for the document—for instance, a journal paper format single-spaced in two columns, as opposed to a first draft double-spaced in one column. With an email that you have to draft and proofread in the same sitting, you might try proofreading a printout of the email. Another trick, which my wife uses, is to highlight the email with her cursor as she proofreads. The highlighting shades the background and gives the words a different appearance. For your most important documents such as an important proposal, you should try to find at least two conscientious readers. If an ambiguity exists, chances are that one of them will catch it.


  1. 1.
    Robert Graves and Alan Hodge, The Use and Abuse of the English Language (New York: Marlowe & Company, 1995), p. 95.Google Scholar
  2. 2.
    e. e. cummings, “Buffalo Bill’s,” Complete Poems: 1904–1962, ed. by George J. Firmage, (New York: W. W. Norton & Company, 2016).Google Scholar
  3. 3.
    Luis García [GFDL ( or CC BY-SA 3.0 (], via Wikimedia Commons.
  4. 4.
    Robert F. Gunning, “The Fog Index after Twenty Years,” Journal of Business Communication, vol. 6, no. 2 (1969), pp. 3–13.Google Scholar
  5. 5.
    H. W. Fowler, A Dictionary of Modern English Usage, 2nd ed. (Oxford: Oxford University Press, 1965).Google Scholar
  6. 6.
    Theodore Bernstein, The Careful Writer, 2nd ed. (New York: Free Press, 1995).Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.College of EngineeringPenn State UniversityUniversity ParkUSA

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