10 Tips for Using Abbreviations Correctly

"Provided they are not obscure to the reader, abbreviations communicate more with fewer letters. Writers have only to ensure that the abbreviations they use are too well known to need any introduction, or that they are introduced and explained on their first appearance."

—From "The Cambridge Guide to English Usage" by Pam Peters

Despite what you may have heard in school, abbreviations, acronyms, and initialisms are commonly used in formal writing (though you'll find them more frequently in business and the sciences than in the humanities). Exactly how they should be used depends on your audience, the country you're living in (British and American conventions differ), and the particular style guide you're following.

10 Tips for Using Abbreviations Correctly

1. Using Indefinite Articles Before Abbreviations, Acronyms, and Initialisms: The choice between "a" and "an" is determined by the sound of the first letter in the abbreviation. Use "a" before a consonant sound (for example, "a CBC documentary" or "a U.S. official"). Use "an" before a vowel sound ("an ABC documentary" or "an MRI").
2. Placing a Period at the End of an Abbreviation: In American usage, an abbreviation that includes the first and last letters of a single word (Doctor, for example) is usually followed by a period (Dr.), while In British usage, the period (or full stop) is usually omitted (Dr).
3. Abbreviating the Titles of Doctors: For medical doctors, write either Dr. Jan Jones or Jan Jones, M.D. (Don't write Dr. Jan Jones, M.D.) For nonmedical doctors, write Dr. Sam Smith or Sam Smith, Ph.D. (Don't write Dr. Sam Smith, Ph.D.)
4. Using Common Abbreviations: Certain abbreviations are never spelled out: a.m., p.m., B.C. (or B.C.E.), A.D. (or C.E.). Unless your style guide says otherwise, use lower case or small capitals for a.m. and p.m. Use capital letters or small caps for B.C. and A.D. (the periods are optional). Traditionally, B.C. comes after the year and A.D. comes before it, but nowadays the abbreviation commonly follows the year in both instances.
5. Abbreviating Months and Days: If the month is preceded or followed by a numeral (14 Aug. or Aug. 14), abbreviate months as follows: Jan., Feb., Mar., Apr., Aug., Sep. (or Sept.), Oct., Nov., Dec. Don't abbreviate May, June, or July. As a general rule, don't abbreviate the month if it appears alone or with just the year—and don't abbreviate the days of the week unless they appear in charts, tables, or slides.
6. Using the Abbreviation Etc.: The Latin abbreviation etc. (short for et cetera) means "and others." Never write "and etc." Do not use etc. at the end of a list introduced by "such as" or "including."
7. Placing a Period After Each Letter in an Acronym or an Initialism: Though there are exceptions, as a general rule omit the periods: NATO, DVD, IBM.
8. Punctuating an Abbreviation at the End of a Sentence: Use a single period when an abbreviation appears at the end of a sentence. The single period does double duty—marking the abbreviation and closing the sentence.
9. Avoid RAS Syndrome: RAS syndrome is a humorous initialism for "Redundant Acronym (or Abbreviation) Syndrome syndrome." Avoid redundant expressions such as ATM machine and BBC corporation.
10. Avoid Alphabet Soup: Alphabet soup (a.k.a. initialese) is a metaphor for using an overabundance of abbreviations and acronyms. If you're unsure whether the meaning of an abbreviation is familiar to your readers, write out the entire word.