As already learned in the earlier modules, A is used before nouns beginning with a consonant sound. An is used before nouns beginning with a vowel sound. It is also important to note that - A and an are usually not used before proper nouns.

For example, A Tajmahal, or An India is grammatically wrong usage of the article.

In this blog, let us learn about some rules, regarding the usage of indefinite articles a and an.

Rule 1:

The indefinite article, a or an, is used before a singular countable noun when it is mentioned for the first time.

EXAMPLES:

He saw a cat in the garden.
I took an umbrella to school

Rule 2:

The indefinite article, a or an, is used before a singular countable noun representing a class of things.

For example
A cow is a mammal.

Here article �a� is being used before �mammal�, which is a singular countable noun representing a class of things.

Rule 3:

The indefinite article, a or an, is used in expressions of price, speed, etc.
For example :
Rice costs twenty rupees a kilogram.
I drove the car at sixty kilometers an hour.

Here articles �a� and �an� are used before kilogram and hour, which are representing an expression of price and speed.

Rule 4:

The indefinite article, a or an, is used sometimes before Mr/Mrs/Miss + surname.

For example

A Mr. Smith has come to see you. �A Mr. Smith� means �a man called Smith�; Which implies that he is a stranger to the speaker.

Read More: What are Determiners in English Grammar? Definition, and Examples