Articles

The words A or An  and The are called Articles. They come before nouns. A or An is called the Indefinite Article, because it usually leaves indefinite the person or thing spoken of; as,

A doctor; that is, any doctor.

The is called the Definite Article, because it normally points out some particular person or thing; as,

He saw the doctor; meaning some particular doctor.

The Indefinite Article is used before singular countable nouns, e.g., A book, an orange, a girl, etc.

The Definite Article is used before singular countable nouns, plural countable nouns and uncountable nouns, e.g., the book, the books, the milk, etc.

                                                                         A or An 

• The choice between A and An is determined by sound. Before a word beginning with a vowel sound An is used; as,    an ass, an enemy, an orange, an umbrella, an hour, an honest, etc.

• It will be noticed that the words hour, honest, heir begin with a vowel sound, as the initial consonant  h is not pronounced.
• Before a word beginning with a consonant sound a is used; as, A boy, a reindeer, a woman, etc.
• Some native speakers use an before words beginning with h if the first syllable is not stressed; as, An hotel ( more common; a hotel ), an historical novel ( more common; a historical novel ).