The indefinite article to indicate one object in a class of objects
1. One or some or every or all without specification; SYN. whatever, whatsoever.
2. (In negative statements) Either every little or very great but unspecified.
ETYM Old Eng. one, on, an, as. än.
1. Being one in number--a single unit or thing.
2. Being the single appropriate individual of a kind; only.
3. Used of a single unit or thing; not two or more.
4. Having the indivisible character of a unit; SYN. unitary.
5. Of the same kind or quality.
6. Indefinite in time or position.
7. Particular but unspecified.
8. Being a single entity made by combining separate components.
9. Used informally as an intensifier.