Grammar What Is an Indefinite Article? |
The Blue Book of Grammar and Punctuation

What Is an Indefinite Article?

Indefinite articles are small but integral parts of English grammar. Today we’ll discuss what an indefinite article is and how it serves communication.

What Is an Indefinite Article?

An indefinite article is simply the word “a” or “an” used before a noun. It denotes the class to which a noun belongs but does not make the noun particular.


Ted went to a store this afternoon.

Ted saw an octopus at the aquarium.

As you can see, an indefinite article tells us about something that isn’t specific. In the first sentence, Ted went to a store, but we don’t know which exact store it might have been. In the second sentence, Ted saw an octopus, but we don’t know if it was a particular octopus or the only one.

By comparison, we might write:

Ted went to his store this afternoon.

Ted saw the octopus at the aquarium.

These modifications make the context more definite: We are now referring to a specific store and a particular octopus. Rather than going to an unknown store, Ted went to the one that he owns. Rather than catching sight of one octopus out of potentially several, he saw the one octopus at the aquarium.

Choosing the Right Indefinite Article

Our discussion of indefinite articles should also clarify how to choose the right one in a sentence.

Although a and an mean the same thing, their inclusion depends on the noun or pronunciation that follows. The indefinite article a is typically used before words that begin with a consonant. The indefinite article an is preferred before words that start with a vowel or a vowel sound.


a bird (indefinite article precedes a consonant)

an open field (indefinite article precedes a vowel)

an MBA (indefinite article precedes a consonant letter pronounced individually as a vowel sound beginning an initialism)

For words and pronunciations that include a first-letter h, we will mainly use a if the h sound is hard and an if the h sound is soft.

Thomas just said he’s going to buy a horse. (hard h sound)

Tell them I’ll be there in an hour. (soft h sound)

Her last name starts with an H. (soft h sound)

In sum, simply remember that the indefinite articles a and an identify nonspecific nouns. Which one we use depends on whether the following noun begins with a consonant, a vowel or vowel sound, or a soft or hard h sound.

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