The indefinite article: 'a' and 'an'

We use the indefinite article, a/an, with singular nouns when the listener/reader does not know exactly which one we are referring to:

Police are searching for a 14-year-old girl.

We also use it to show that the person or thing is one of a group:

She is a pupil at London Road School.

 We use a before a consonant sound:

a banana (starts with /b/)

a university (starts with /j/)

and an before a vowel sound:

an orange (starts with /o/)

an hour (starts with /au/)

Note that the choice of a or an depends on sound, not spelling.

We do not use an indefinite article with plural nouns or uncount nouns:

She was wearing blue shoes. (plural noun)
She has short, blonde hair. (uncount noun)

EXERCISES 

EXERCISE 1:  Articles(A, An, The)

EXERCISE 2: The indefinite article 1