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When to Use A vs An | Rules, Difference & Examples

When to Use A vs An | Rules, Difference & Examples

Commonly Confused Words updated on November 21, 2023 4 min read

A and an are two forms of the indefinite article that’s used before a noun.

You use a before a word that starts with a consonant sound (e.g., “b,” “f,” or “t”).
You use an before a word that starts with a vowel sound (e.g., “i,” “e,” or “a”).

When you’re trying to determine whether to use “a” or “an,” you should pay attention to the sound the noun starts with, not its spelling. For example, “hour” is spelled with a consonant at the beginning, but it is pronounced like the word “our.” This means that it starts with a vowel sound and requires the indefinite article “an.”

Examples: A in a sentence	Examples: An in a sentence
I ate a banana before going on a walk.	It’s an honor to meet you.
He is a student at Harvard.	I want to bake an apple pie for my birthday.
I would like to speak to a union representative.	I am happy I brought an umbrella on our walk.

Note
The form of the indefinite article depends on the initial sound of the word that comes directly after it. This is often a noun, but it can also be an adjective.
✓ An orange
✗ An sweet orange
✓ A sweet orange

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A or an before U

For words beginning with “u,” you should consider the way the first letter sounds.

If the “u” sounds like “uh,” use “an” (e.g., “an understatement,” “an ultimatum”).
If the “u” sounds like “you,” use “a” (e.g., “a utopia,” “a university”).

Examples: A or an before u
My aunt swears that she spotted a UFO in her early twenties.
Mother and baby are connected through an umbilical cord.
My aunt wants to throw a unique party when she turns forty.
I think your computer broke down because you missed an update.

A or an before H

For words beginning with “h,” you also have to consider the way the first letter of the word sounds.

If the “h” is silent and followed by a vowel sound, you use “an” (e.g., “an heirloom,” “an hourglass”).
If the “h” is pronounced, you use “a” (e.g., “a heart,” “a hammer”).

Examples: A or an before h
She arrived at the airport an hour before her flight.
Mary and Lucas bought a house last year.
He asked the organization for an honorarium to cover his travel expenses.
Rowan received a discount because he is a hospital staff member.

A or an before an acronym

If you’re unsure whether an acronym should be preceded by “a” or “an,” say the acronym out loud to determine whether it starts with a consonant or vowel sound.

For acronyms that start with a consonant sound, you use “a.”
For acronyms that start with a vowel sound, you use “an.”

Some acronyms are pronounced as full words (e.g., “NATO”), while you pronounce others by saying the individual letters. If an acronym beginning with a consonant is pronounced with an initial vowel sound, you still have to use “an.” One example is the letter “s” (pronounced [es]).

Examples: A or an before acronyms
Mabel called in sick to work because she has a UTI.
Lovine is an FBI agent in Chicago.
The family decided to buy an SUV for their road trips.
My brother sent a GIF in the family group chat.

Common mistakes	Commonly confused words	Rhetoric
Whoa or woah	Advisor vs adviser	Metonymy
Theirs or their's	Accept vs except	Synecdoche
Ours or our's	Affect vs effect	Verbal irony
Forty or fourty	Among vs between	Irony
Sence or sense	Anymore vs any more	Grawlix

Frequently asked questions about a vs an

Is it an historic or a historic?

There are two variants of the indefinite article: a and an. You use “a” when the word starts with a consonant sound and “an” when the word starts with a vowel sound.

The word “historic” can be pronounced with a hard “h” (consonant sound) or silent “h” (vowel sound). You should choose the indefinite article that fits your pronunciation.

I watched a historic movie.
I watched an historic movie.

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Is it an hour or a hour?

There are two variants of the indefinite article: a and an. You use “a” when the word starts with a consonant sound and “an” when the word starts with a vowel sound.

The noun “hour” is pronounced with a silent “h” (vowel sound), so you should use “an.

We only have a hour.
I waited an hour for you.

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Is it an unique or a unique?

There are two variants of the indefinite article: a and an. You use “a” when the word starts with a consonant sound and “an” when the word starts with a vowel sound.

The “u” in “unique” is pronounced like the word “you,” which is a consonant sound. This means you should use “a.”

An unique watch
A unique personality

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Is it an honor or a honor?

There are two variants of the indefinite article: a and an. You use “a” when the word starts with a consonant sound and “an” when the word starts with a vowel sound.

The word “honor” is pronounced with a silent “h” (vowel sound), so you should use “an.”

It’s a honor to meet you
It’s an honor to meet you.

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Julia Merkus

Julia has master's degrees in Linguistics and Language and speech pathology. Her expertise lies in grammar, language and speech disorders, foreign language learning, and child language acquisition.

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