Abbreviations are a sometimes necessary evil, but with the power to employ them comes great responsibility. This post outlines types of abbreviations and associated guidelines.
An abbreviation is a shortening of a word or phrase, either by truncation or by abridgement by way of using only the first letter of each word of the term in turn (though sometimes more than the first letter is included, and occasionally, in the interest of creating an easily pronounceable abbreviation, one or more words are not represented).
In the case of truncation, a word is whittled down to the first letter or first several letters, or the first and last letters (and sometimes others). Thus, L or R might be used in place of left or right as a directional indicating positioning of people, place, or things in a caption for a photograph or other figure. Job titles are often abbreviated to the first few letters of a word as in military ranks (major and gen. for major and general) and political offices (sen. and rep. for senator and representative). Exceptions in the former category include sgt. for sergeant and capt. for captain.
In American English, abbreviations for social titles usually reduce a word to its first and last letters, followed by a period, as in the case of Mr. and Dr., and common abbreviations follow this form (as in the case of hr. for hour, though the abbreviations for second and minute are the truncations sec. and min.).
Two other types of abbreviation are the acronym and the initialism. In both categories, a string of words is reduced to (usually) the first letter of each word; the distinction is that an acronym, as the element -onym (Greek for “name” or “word”) indicates, is pronounced as a word, as in the case of NASA, whereas an initialism, as the name suggests, is sounded out letter by letter, as in FBI.
Most people are not aware of (or do not give any thought to) the distinction, but it is important in this sense. Because acronyms are treated as words, they are not preceded by an article (one writes “NASA was established in 1958,” not “The NASA was established in 1958”); by contrast, an article precedes an initialism (as in “The FBI launched the investigation in January,” not “FBI launched the investigation in January”). Exceptions occur when an acronym is used adjectivally (“The NASA project is underway”) and in periodical headlines (“FBI Launches Investigation”).
In American English, acronyms and initialisms are often distinguished by styling the former in small caps and the latter in full-size capital letters, though abbreviations of more than four letters are often, after long usage as capitalized terms, treated as regular words, as in the case of Nasdaq, a proper noun (an abbreviation of “National Association of Securities Dealers Automated Quotations”) and radar (from “radio detection and ranging”).
Unfamiliar acronyms and initialisms are usually introduced to readers in parentheses immediately after the first reference to the entity by its full name, after which the abbreviation alone is sufficient (or the abbreviation is simply used after the first reference without the parenthetical signal, as long as the next reference appears soon after the first one), but common abbreviations need no such introduction. However, whether an abbreviation is considered transparent or otherwise is up to a specific publication or publisher to decide, based on its readership’s familiarity with the term. (Companies should keep a record of such usage in a house style guide; see also this post.)
Another consideration, though, is to avoid cluttering a piece of writing with numerous abbreviations, which smacks of jargon. If a term is used only occasionally, it may be better to spell it out in each case. Another strategy to avoid frequent repetition of acronyms or initialisms is to sometimes replace the term with a generic reference such as “the agency,” “the law,” “the program,” and so on.
Writers should avoid redundancy in using acronyms and initialisms, where widespread usage obscures the wording of the phrase from which the abbreviation is formed, so that reference is too often made to, for example, ATM machines (the M stands for machine) and PIN numbers (number is represented by the N).
A variation of use of acronyms is syllabic abbreviation, in which terms consist of parts of, or one or more syllables of, one or more words; examples include Interpol (“international police”) and nicknames for urban areas such as SoHo (denoting “south of Houston Street”) in New York City.
In general, lowercase abbreviations include periods (as in the case of i.e., a.m., and m.p.h.), and uppercase abbreviations omit them (as with MD, US, and ABC). However, specialized publications, especially those pertaining to science and technology, often do not use periods in either case, and note that shorthand for metric terms is considered a system of symbols rather than abbreviations, so periods are never used with cm (centimeter) or kg (kilogram), for example.
Certain treatments of initials in names are treated differently in some publications: According to The Chicago Manual of Style, the style guide of record for most book publishers and many publications, a letter space should separate two or more initials in a name, as in “A. B. See.” However, the Associated Press Style Book avoids spaces when possible, including in names. Initials used in lieu of an entire name, such as those for famous politicians and other public figures, are universally formatted without spaces or periods, as in JFK and MLK.
Most publications and publishers do not use apostrophes when pluralizing an abbreviation, as in PCs and URLs. For some specialized terms, such as abbreviated terms for units of measure, no plural is indicated in the abbreviation (so, for example, lb. applies to one or more pounds); another exception is abbreviations in baseball: “Runs batted in,” for example, is abbreviated as RBI.
Use of informal abbreviation (lulz and the like) has proliferated since the advent of online social media, but this trend has not been accepted into formal usage and should be avoided except in casual writing and in communication among family and friends.