!!! 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)