GrammarPhile Blog

When to Use “A” vs. “An”

Posted by Sara Richmond   Apr 7, 2022 7:30:00 AM

What’s the rule?

I have an incredibly smart friend who believed that onions should never be refrigerated.

He’d read something online that claimed if you stored a raw onion in a refrigerator, it would absorb toxic bacteria and poison you. I informed him that onions often require cold temperatures to grow properly, so that claim made absolutely no sense. And for all the refrigerated onions my family had eaten, we’d never once been ill. He laughed.

Sometimes we’re fed a partial truth (that whole onions are better stored outside the refrigerator, for example) and ingest it as a whole one (it’s dangerous to store onions in the refrigerator). Just like the commonly known rule for using “a” and “an.”

If you were told in elementary school to use “a” before words beginning with a consonant and to use “an” before words beginning with a vowel, you were on the right track. But the truth is a little more complicated, and it can come back to bite you in the onion.

Let’s start at the beginning before we move forward. You already know the following examples are correct.

  • An apple bonked me on the head
  • A ball in the shape of an onion
  • An elephant
  • A helicopter for ants (what my daughter calls dragonflies)
  • An igloo
  • A hoax about onions ruined his life
  • That was an exaggeration
  • An urban myth about onions being stored in the refrigerator

Now here’s the all-important clarification of the “a” and “an” rule:

Use “a” before words that begin with a consonant sound and use “an” before words that begin with a vowel sound. The key addition is “sound.”

Based on that, take a look at these examples, which are also correct:

  • A university
  • An honor
  • An “m” is missing from the street sign
  • A yak ate my homework
  • A urologist appointment is my least favorite thing
  • An “l” is missing from her name
  • An hour is 60 minutes long
  • An em dash is my favorite punctuation mark
  • An M.A. in biology

If you’re confused, repeat the list aloud, focusing on the first sound you hear as you pronounce the word after the articles “a” or “an.”

Now look back at the list as you read these explanations:

  • The word “university” begins with a long “u;” the initial sound as it’s pronounced is a consonant “y,” just like the word “you.” That’s a beginning consonant sound. So we use “a.”
  • The letters “l” and “m” are pronounced with a beginning short “e” sound. Both require “an.”
  • “Y” can operate as a vowel or a consonant sound. Though “y” most often makes a vowel sound (short “i” as in “cylinder,” long “i” as in “cycle,” and long “e” as in “happy”), if it’s at the beginning of a word, it’s always working as a consonant (true for English, not so true for other languages, of course). That’s why I included “a yak.” Don’t be fooled by this tricky and flexible letter!
  • Some words, such as “honor” and “hour,” begin with a silent consonant, so we hear a vowel sound first.* In those cases, we use “an.”

You don’t need to understand the reasons behind all these pronunciation/spelling quirks; you only need to know how to say the words and apply the simple rule.

To summarize:

  • Consonant sound first = “a.” Vowel sound first = “an.” Beginning sound is king.
  • If this is an “I was today years old when I learned this rule” moment, it doesn’t mean you’re dumb. Remember the onion friend.
  • Old habits die hard. That friend still keeps his onions on the counter. So if you find yourself making a mistake, just reiterate the more accurate rule in your brain and keep on waltzing.

If you have more questions about this rule, submit a comment below. And if you’re feeling pretty confident after reading this post, see if you can ace this grammar quiz from the ProofreadNOW archives.

We’re cheering you and your grammar game on!



*Silent consonants are sometimes based on the dialect of a region. If it’s more common to pronounce a silent letter at the beginning of a word where you live (e.g., (H)umble, Texas), adjust your articles accordingly with our blessing.


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