Semantic and syntactical ambiguity
A sentence is ambiguous when it can be read in more than one way. The ambiguity comes either from a word that has more than one meaning or from a structure that can be broken into its parts in more than one way, and settling it takes information from outside the sentence, some of which, such as tone of voice, is lost when the sentence is written down. Both kinds can arise in a noun string, a series of words that modify a final noun.
What ambiguity is
If the king exclaims "The peasants are revolting!", he could be expressing his contempt for the peasantry or his alarm that they are rising up against him, so the exclamation is ambiguous. Ambiguous comes from a Latin word that originally meant to drive in both directions and is often used to describe a word or sentence that can be interpreted in two or more ways; it can also convey that something is doubtful or uncertain, especially because it is obscure or indistinct. Poets often use ambiguity deliberately, for poetic effect, and comedians for comedic effect, but medical communicators must avoid it; they do not want to confuse or mislead their readers.
Two kinds of ambiguity
Ambiguity in a sentence can result from two different kinds of problem: semantic ambiguity results from a word having more than one possible meaning, and syntactical ambiguity results from a problem in the structure of the sentence. Semantic ambiguity is a common problem in medical writing; for example, the word nursing could refer to the duties of a nurse, but it could also mean breastfeeding. An even more common word that can be ambiguous is since, which originally meant after but can also imply a cause-and-effect relationship.
The king's exclamation combines the two. The verb revolt means to renounce allegiance or subjection, so if are revolting is the present progressive of to revolt, the peasants are currently rising up against their oppressors; but revolting can also be an adjective meaning extremely offensive or distasteful. Which meaning a reader takes depends on how they parse the exclamation, that is, break it down into its parts of speech: as the present progressive of to revolt, or as a linking verb, are, and an adjective serving as a predicate complement.
Context, and what writing loses of it
By itself, the king's statement does not give enough information to decide which meaning of revolting was meant, and clearing up the confusion takes information from outside the sentence: its context. Context came from the Latin contextus, which in turn came from a word meaning weaving together, so it can refer to the parts of a discourse that surround a word or statement, and also to the environment or setting in which something happens.
For someone present when the king speaks, his facial expression and tone of voice would probably clear up the ambiguity: is his nose wrinkling in disgust, or are his eyes wide with fear? Facial expressions, tone of voice and prosody (rhythm and intonation) are lost when a sentence is written down, so writers must be particularly careful to avoid writing sentences that could be misconstrued.
In good technical writing, the meaning of each sentence is clear and unambiguous, and ideally it should be immediately obvious. The reader should not have to waste time and energy puzzling out the meaning of ambiguous sentences from their context.
Why English is prone to syntactical ambiguity
English is particularly prone to syntactical ambiguity because it is an analytic language, with remarkably few inflections. The ending of a noun does not change to indicate whether it is the subject of a verb, the direct or indirect object of a verb, or the object of a preposition. Nouns and adjectives are not marked for gender or case, and adjectives are not marked for number. Some nouns can be used as if they were adjectives (attributive nouns), some nouns can be used as verbs, and some verbs as nouns. To avoid syntactical ambiguity, a writer has to pay careful attention to word order and the use of prepositions.
John is closer to his mother than his father would not be ambiguous in Latin, which declines nouns for case. In English, because of the lack of inflection, the reader cannot tell which relationships the writer intends to compare.
Noun strings
A noun string is a series of nouns and other words that somehow modify the final noun, as in "digital toilet paper coupons". That string is ambiguous both ways: semantically, because digital can refer to numbers or to fingers, and syntactically, because digital could modify coupons or toilet paper.
Noun strings can be hard to read, partly because they are hard to parse: the reader has to break the phrase down into its parts of speech and work out how those words relate to each other syntactically. Because English has so few inflections, a noun string does not always give enough grammatical clues to allow the reader to parse it correctly. Noun strings are common in technical writing because they can be a terse way to express a complex idea, and some writers frequently use them on purpose to minimise word count. They are often ambiguous and can therefore be misread, and even one that cannot be misread may be hard to parse. Forcing a reader to slow down to parse a noun string interrupts the flow of information into the reader's mind, and it would be better to break up the string so that the meaning of the text is immediately clear.
One experienced medical copyeditor thinks about ways to break up any noun string longer than three words, with these tips:
- Find the main noun, which is usually at the end of the string.
- Omit needless words.
- Hyphenate compound modifiers.
- Add some prepositions and articles if necessary.
- Consider turning some nouns into a verbal form.
- Consider using the possessive form of some nouns.
- Consider using abbreviations.
- Try to think of a single word that can replace a string of words.
There can be more than one way to fix a noun string. In "a hospital patient health and wellbeing monitoring scheme", the main noun, scheme, is at the end of the string, and prepositional phrases break it up: "a scheme for monitoring the health and wellbeing of hospitalized patients". To avoid a monotonous string of prepositional phrases, a possessive can be used: "a scheme for monitoring hospitalized patients' health and wellbeing". In "real-time ultrasonographic blood flow detection techniques", the main noun, techniques, is also at the end, and because real-time refers to the timing of the detection, the rewrite associates it with detection rather than with ultrasonographic: "ultrasonographic techniques for real-time detection of blood flow". In "employee competence level evaluation procedures", the noun evaluation is turned into the participle evaluating: "procedures for evaluating employees' competence". "An over-the-counter drug adverse events monitoring program", which contains the prepositional phrase over the counter, becomes "a program for monitoring the adverse events associated with over-the-counter drugs", or, if the abbreviation OTC cannot be used, "a program for monitoring the adverse events associated with nonprescription drugs".
A writer who parses their own writing can identify and remove ambiguous noun strings, which clarifies the meaning and improves the flow of information to the reader.
Reducing ambiguity in one's own writing
A writer can do three things to reduce ambiguity: study a dictionary, study the AMA Manual of Style, particularly its section on correct and preferred usage, and learn how to diagram sentences. A dictionary alerts the writer to words that have more than one meaning. The AMA style manual alerts the writer to many ambiguous words and syntactical problems, especially those that occur frequently in medical writing. Diagramming sentences helps the writer identify many syntactical problems that affect the meaning of their sentences.