ETYM Old Eng. one, on, an, as. än.
(Homonym: won).
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.

1. A single person or thing
2. The smallest whole number or a numeral representing this number; SYN. 1, I, ace, single, unity.

1. A certain indefinitely indicated person or thing
2. An individual of a vaguely indicated group; anyone at all — used as a third person substitute for a first person pronoun
3. A single instance of a specified action