When to Use A or An

Instructor: David Boyles

David has a Master's in English literature. He has taught college English for 5+ years.

The articles 'a' and 'an' perform a similar job in sentences. So how do you know which one is right in any given situation? This lesson will walk you through the process of figuring that out.

The Articles

'A,' 'an,' and 'the' make up a special class of English words known as articles. These three words are used in front of a noun (person, place, or thing) to indicate the type of reference being made to that noun.

The articles are especially tricky for writers, readers, and speakers whose first language is not English, since many languages around the world do not even have articles. But once you know a couple of simple rules, it is easy to know how to use them.

Definite and Indefinite Articles

The first thing to know when deciding to use 'a' or 'an' is the difference between a definite articles and indefinite article. 'The' is a definite article, used to refer to a specific person place, or thing:

  • The house on the right is mine.
  • That is the guy who robbed me.

'A' and 'an,' on the other hand, are indefinite articles. They are both used to describe one of many people, places, or things:

  • I went to a great party last night.
  • My dog is an Irish setter.
  • I bought a cheeseburger at In N Out.
  • Dr. Jones is an esteemed scientist at Yale University.

In all of these sentences, 'a' or 'an' is used to refer to one of many possible parties, Irish setters, cheeseburgers, and scientists. So, this is the first thing to decide. Are you referring to a specific noun or one of many nouns. If it is one of many, you need to use 'a' or 'an.' But which one? Let's find out.

First Letter

The difference between 'a' and 'an' is determined entirely by the first letter of the word that immediately follows it. If the word immediately following starts with a vowel (the letters a, e, i, o, u), use 'an.' If it starts with a consonant, use 'a.'

The word immediately following it is usually either the noun or an adjective (describing word) that is describing the noun. Let's take a closer look at our examples from the previous section that used 'a:'

  • I bought a cheeseburger at In N Out.

In this sentence, the word right after the article is the noun 'cheeseburger.' 'C' is a consonant, so we used 'a.'

  • I went to a great party last night.

In this example, the word after the article is an adjective, 'great.' But it also starts with a consonant, so we still use 'a.'

Now let's look at the sentences that use 'an.'

  • My dog is an Irish setter.

'Irish setter' is the name for a breed of dog, so it's a noun. And it starts with a vowel, 'I,' so we use 'an' before it.

  • Dr. Jones is an esteemed scientist at Yale University.

In this case, the adjective 'esteemed' comes after the article, but it starts with an 'e,' so we still use 'an.'

The 'H' Exception

One thing that often trips people up on using 'a' and 'an' is words that start with 'h.' In several words that start with 'h,' such as 'honest,' 'herb,' and 'honor,' the 'h' is not pronounced, so the first sound you hear when saying the word is the vowel. For these words, it is generally accepted to use 'an' instead of 'a,' even though the first letter is technically a consonant:

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