<unk>  is the chemical process resulting in the removal of a methyl group (CH3) from a molecule. A common way of<unk>  is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms. The counterpart of<unk>  is methylation.
Demethylation
Hydrolysis
Hydroxylation
Acetylation
Flagging 
Glucuronidation
Phosphorylation
Fragmentation 