English Grammar. Indefinite Articles: A and An

Blog Image

Indefinite articles are used when we are referring to an unspecified thing or quantity. We use them when we don’t know (or don’t care) which thing we’re talking about.

There once was a sheep.

Since I don’t know which sheep it was—that is, I don’t know its name, where it’s from, or anything about it — I can’t say the sheep.

How to Use the Indefinite Articles A vs. An

The two indefinite articles in English are a and an. The indefinite article an is used to make pronunciation easier when reading a text aloud. The general rule is to use a when the indefinite article precedes a word beginning with a consonant sound and an when it precedes a word starting with a vowel sound.

1. Use a when the indefinite article comes before a word beginning with a consonant sound: a toy, a book, a house

2. Use an when the indefinite article comes before a word beginning with a vowel sound: an operation, an idea, an apple



It’s important to note that not all nouns that begin with a consonant begin with the consonant sound. Always trust the sound, not the letter when applying the a vs. an rule. Remember, it’s about pronunciation. Consider the examples below:

a hourglass (incorrect)

an hourglass (correct)

a honor (incorrect)

an honor (correct)

Likewise, there are some nouns beginning with a vowel that make a consonant sound. In these cases, the indefinite article a should be used:

an university (incorrect)

a university (correct)

an one-eyed pirate (incorrect)

a one-eyed pirate (correct)

Using A vs. An with Acronyms

These same rules apply to acronyms:

A Society of Writers member was quoted in the article. (correct)

A S.O.W. member was quoted in the article. (incorrect)

An S.O.W. member was quoted in the article. (correct)

Because S sounds like it begins with a vowel (ess), an should be used in front of it. 


Learning English will improve your chances of Getting a better Job, Earn More Money, Travel Abroad, Study Internationally & Make new international Friends
Start Learning your first English lesson within 5 Minutes!

Registered Students
Language Certificates
Satisfaction Rate

Great site to keep my english skills updated for work and travel. I am really enjoying the lessons!

Maria C
ar   Argentina

Loved the course. Abitlity to improve my grammar and spelling in a step by step method has really helped me. Thanks!

Andre T
fr   France