0 used before a noun to refer to a single thing or person that has not been mentioned before, especially when you are not referring to a particular thing or person: --
1 one: --
2 written abbreviation for amp --
3 in or for each or every; per: --
4 the first letter of the English alphabet --
5 in Western music, the sixth note in the scale (= series of notes) that begins on the note C, or a set of notes based on this note --
Colin told a joke about a postman, but it wasn't very funny.
The customer said she'd like this coat if it was a nicer colour.