Article

An article is a kind of adjective which is always used with and gives some information about a noun.  There are only two articles a (or an)and the, but they are used very often and are important for using English accurately.
         
The is called the definite article because it refers to a particular person or thing in the sentence.

EX.— The woman walks.
EX.— The girls play.
EX.— The dog runs.
       
In these sentences we refer to a particular woman, girl, and dog with a definite article. The definite article is used both with singular and plural forms of the noun.

The indefinite article a (or an) indicates any one of the things for which the noun stands.

EX.— A girl, a car, a computer .

A is used before words beginning with a consonant sound, including h, a long u or eu, and before one, once.

EX.— a house, a car, a historical fact, a beer, a long passage, such a one, a once popular singer.

EX.— An hour, an instant, an order, an apple, an urgent request, an evening, an honest person.

NOTE— An is used before words beginning with a vowel sound. , e.g., an eye, an eagle, an oyster, an envelope.