Have you ever heard someone refer to “an historic occasion” and wondered whether they were right or wrong about that “an”? Keep reading for the easy rule that will let you know what’s what.
(Bonus tip: A, an, and the—those common words we use before nouns—are known as “articles.” Today we’re talking about just two of the articles: a and an.)
At the most basic level, an is the article we use before words that start with vowels (a, e, i, o, u). A is the article we use before words that start with consonants (the other 21 letters!).
- a squirrel, a chipmunk, a hedgehog
- an otter, an emu, an elephant
But—SPOILER ALERT—that’s not the whole story! Plot twist ahead.
If this rule were all we had to consider, then we’d say, for example, “It was a honor to be asked to give an eulogy for the late mayor.”
That probably sounds off to you (good ears!), but why? After all, honor begins with a consonant, so shouldn’t it be preceded by “a”? And eulogy begins with not just one vowel but two (two!), so shouldn’t we start off with “an”?
The Chicago Manual of Style (CMS, paragraph 5.72) articulates what’s really going on here:
The choice of “a” or “an” depends on the sound of the word it precedes. “A” comes before words with a consonant sound . . . no matter how the word is spelled. . . . “An” comes before words with a vowel sound.
An comes before vowel sounds. A comes before consonant sounds.
- Honor is pronounced with an o sound first, thus we say, “an honor.”
- Historic is pronounced with a “huh” h sound first, thus we should say “a historic occasion” NOT “an historic occasion.”
This even applies for acronyms, as CMS points out:
- an LSAT exam room: pronounced “ell sat,” starting off with an e sound
- an X-Files episode: pronounced “ex files,” again with that leading e sound
One final note: some of you have heard the letter y referred to as a “sometimes” vowel because it sometimes represents a vowel sound (i or e) as in sylph and funny. When the letter y makes a “yuh” sound, as in you and yours, we treat it as a consonant. With a vowel sound—as in, say, Ypsilanti—we treat it as a vowel.
Thus: I spent a year of bliss working in an Ypsilanti donut-tasting facility. Aha!
Your rule of thumb for a and an is to trust your ears more than your eyes.
Here’s to the next draft!
Got a burning question about writing rules or best practices? Drop me a note at firstname.lastname@example.org or reach out on Twitter or Facebook!