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.
Indefinite Articles: A and An
A
A house
A book
A toy
Use a when the indefinite article comes before a word beginning with a consonant sound
Subtopic
An
Examples:
An apple
An idea
An operation
Use an when the indefinite article comes before a word beginning with a vowel sound
