I have a distinct childhood memory of learning that we say "an apple," not "a apple." Most of us learned how to choose between "a" and "an" in our early years. But as adults, many of us misremember or overthink the rule, leading to grammatical errors.

 

Choosing between the indefinite articles "a" and "an" is actually quite simple. It depends on only one thing: how the next word is pronounced.

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Here's the rule: 

Use "a" before words beginning with a consonant sound.

Use "an" before words beginning with a vowel sound.

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Notice that I said "consonant sound" and "vowel sound." All that matters is how the word is pronounced, not what letter it starts with.

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Let's go over some examples.

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Use "a" before words like these that begin with a consonant sound:

• a butterfly

• a newspaper

• a university

• a European vacation

• a one-way street

• a happy occasion

• a historic day

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Remember that it doesn't matter what letter the word starts with. Focus only on the first sound of the word. "University" and "European" both start with the "y" consonant sound, so we use "a" before them. The same goes for "one-way street," which begins with the "w" consonant sound. "Happy" and "historic" both start with pronounced "h" consonant sounds, so "a" is the correct choice for these words too.

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"But wait—I hear people on TV all the time saying 'an historic moment' or 'an historic day,'" you may be thinking. "Even news anchors and late night hosts with teams of professional writers! They can't be wrong, can they?"

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Sadly, my friends, they are wrong. It is simply incorrect to use "an" before a pronounced "h" like in the American pronunciation of "historic." (The Chicago Manual of Style agrees: "The indefinite article a, not an, is used in American English before words beginning with a pronounced h.")

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But I digress. Let's look at some examples that use "an" before words beginning with a vowel sound:

• an apple

• an ice cream cone

• an umbrella

• an hour

• an heir

• an honor

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The "h" in "hour," "heir," and "honor" is silent, so these words all begin with a vowel sound. That's why we need to use "an" before them. 

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Aside from "h" words, some people also get confused about which indefinite article to use before acronyms and initialisms, or phrases beginning with numbers. But the rule remains the same: All that matters is how the word is pronounced.

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So we say:

• a NASA program

• a FICO score

• a 60-year-old man

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But we say:

• an NGO

• an FDA regulation

• an 80-year-old woman

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Pronouncing two vowel sounds in a row is hard. That's why we use "an" before words beginning with vowel sounds. So if you're ever unsure which indefinite article to use, just sound it out, and you'll never mix up "a" and "an" again!

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