Definite and indefinite articles: the, a, an

The definite article the as a determiner can be used before singular or plural nouns such as people or things, and before countable and uncountable nouns.

We use the determiner the:

to refer to people or things which we know because they have already been mentioned.

to refer to a person or thing when there is only one.

before superlatives, words such as firstonly, etc.

before adjectives so that the adjectives become nouns. 

before a singular noun that is representative of a group of similar people or things.

before proper nouns.


We use the determiners a/an:

to refer to someone or things that we know nothing about as they have not been mentioned before, or they are not particular persons or things.

before an uncountable noun.

before an action noun.

before a quantity.

before a proper noun such as a person’s name.