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LawProse Lesson #132: What is the right way to use articles before abbreviations? EPA or the EPA? An HMO or a HMO?

There is no single “right” answer to this question. Conventional usage prevails. EPA is more common than the EPA when it’s standing alone (more on this below). But HMO is very uncommon—as rare as the HBO.

There are two types of abbreviations: acronyms and initialisms. An acronym is made from the first letters or parts of a compound term. It’s read or spoken as a single word (e.g., awol, radar, NASA). An initialism is also made from the first letters or parts of a compound term, but it’s sounded letter by letter (e.g., ATM, SUV, NBA).

Acronyms generally are not preceded by an article {history of NASA}, unless they are being used as an adjective {the NASA employees}. With initialisms, it’s common—but not required—to use an article {EPA or the EPA}.

When an indefinite article is needed before the abbreviation, the choice between a and an depends simply on how the first syllable is sounded: the sound rather than the letter controls. Use a before abbreviations beginning with a consonant sound {a UFO} {a PIN} {a CLE program}. Use an before abbreviations that begin with a vowel sound {an FBI agent} {an NRA member} {an SEC report}. Note that an initialism may be paired with a different article from the one used with an acronym that starts with the same letter {an HTML website for a HUD program}.


The Chicago Manual of Style § 7.44, at 362, § 10.9, at 491 (16th ed. 2010).
The Redbook § 12.3, at 246 (3d ed. 2013).
Garner’s Modern American Usage 1, 2 (3d ed. 2009).

Thanks to William L. Berg and John A. Strylowski for suggesting this topic.

Bryan A. Garner, President of LawProse Inc., is the most prolific CLE presenter in the U.S., having trained more than 150,000 lawyers and judges. His book — most prominently Black’s Law Dictionary and Garner’s Modern American Usage — have been cited as authority by every state and federal appellate court, including the highest. For more about him, go to To follow him on Twitter: @bryanagarner.

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