1. Consisting in the absence of something; not positive; negative.
2. Indicating the absence or negation of some quality.
3. Consisting in, or characterized by, the taking away, loss, or lack of something.

In Greek grammar, a prefix having negaitive or privative force, as in atheos, "godless".

A-, an-, as prefixed to terms or stems of Greek or Latin origin, often means "apart from" or "not concerned with"; for example, an amoral approach to economics is one that is "not concerned with moral issues".