Updated: Jul 10, 2021
This articles provides guidance for using abbreviations and symbols in general and scholarly writing. It also offers some guidance in technical work, especially for the generalist editor confronted with unfamiliar terms. For abbreviations not listed here, we recommend Merriam-Webster's Collegiate
ACRONYMS, INITIALISMS, CONTRACTIONS
The word acronym refers to terms based on the initial letters of their various elements and read as single words (AIDS, laser, NASA, scuba); initialism refers to terms read as a series of letters (AOL, NBA, XML); and contraction refers to abbreviations that include the first and last letters of the full word (Mr., amt.). (For the type of contractions normally formed with apostrophes. The definitions are not perfect. For example, sometimes a letter in an initialism is formed not, as the term might imply, from an initial letter but rather from an initial sound (as the X in XML, for extensible markup language), or from the application of a number (W3C, for World Wide Web Consortium).
Furthermore, an acronym and initialism are occasionally combined (JPEG), and the line between initialism and acronym is not always clear (FAQ, which can be pronounced either as a word or as a series of letters). In this chapter the umbrella term abbreviation will be used for all three, as well as for shortened (i.e., abbreviated) forms (ibid., vol., prof., etc.), except where greater specificity is required. (Occasionally, a symbol abbreviates a term, as in Â© for copyright. On the other hand, abbreviations for units are often referred to as symbols in SI usage
WHEN TO USE ABBREVIATIONS
Outside the area of science and technology, abbreviations and symbols are most appropriate in tabular matter, notes, bibliographies, and parenthetical references. Even in regular prose, a number of expressions are almost always abbreviated and may be used without first spelling them out. Many of these will be listed as main entries with pronunciation (rather than as abbreviations) in the latest edition of Webster's (e.g., DNA, GPS, HMO, HTML, IQ, JPEG, laser, Ms., NASA). Others, though in more or less common use (CGI, FDA, HVAC, MLA), should generally be spelled out at first occurrence--at least in formal text--as a courtesy to those readers who might not easily recognize them. The use of less familiar abbreviations should be limited to those terms that occur frequently enough to warrant abbreviation--roughly five times or more within an article or chapter--and the terms must be spelled out on their first occurrence. (The abbreviation usually follows immediately, in parentheses, but it may be introduced in other ways; see examples. Such an abbreviation should not be offered only once, never to be used again.) Writers and editors should monitor the number of different abbreviations used in a document; readers trying to keep track of a large number of abbreviations, especially unfamiliar ones, will benefit from a list of abbreviations.
"A," "AN," OR "THE" PRECEDING AN ABBREVIATION
When an abbreviation follows an indefinite article, the choice of a or an is determined by the way the abbreviation would be read aloud. Acronyms are read as words and are rarely preceded by a, an, or the ("member nations of NATO"), except when used adjectivally ("a NATO initiative"). Initialisms are read as a series of letters and are often preceded by an article ("member nations of the EU").
a NATO member
a LOOM parade
an AA meeting
a AA battery (pronounced "double A")
an NAACP convention
an NBA coach
an HIV test
an MS symptom (a symptom of multiple sclerosis)
a MS by . . . (would be read as "a manuscript by . . .")