The removal of a hydrogen atom on a carbon atom in an organic molecule as a proton results in a species that has a formal charge of -1 on a carbon atom. It is called a carbanion.

eg:

Some carbanions are resonance stabilized, in which case some or all resonance forms fit the above definition.

eg. 1:

eg. 2:

see also alkyl carbanion, aryl carbanion, carbanion equivalent, aryl carbocation