not any particular or certain one of a class or group: a man; a chemical; a house.

a certain; a particular: one at a time; two of a kind; A Miss Johnson called.

another; one typically resembling: a Cicero in eloquence; a Jonah.

one (used before plural nouns that are preceded by a quantifier singular in form): a hundred men (compare hundreds of men ); a dozen times (compare dozens of times ).

indefinitely or nonspecifically (used with adjectives expressing number): a great many years; a few stars.