a と the

a と the

An Article is a word placed before a noun to show whether the latter is used in a particular or general sense.

There are two articles, a or an and the. A or an is called the indefinite article because it does not point out any particular person or thing but indicates the noun in its widest sense; thus, a man means any man whatsoever of the species or race.

The is called the definite article because it points out some particular person or thing; thus, the man means some particular individuals.

(How to speech and write correctly より)