What is "desmethyl"

a. (context organic chemistry in combination English) Used to name organic compounds from which a methyl group has been removed

Desmethyl is a term used in organic chemistry to refer to a methyl group that has been removed. It is often substituted in nomenclature for the more general Nor- prefix, the removal of one carbon atom along with the accompanying hydrogen atoms, however this prefix can be used to refer to two other structure changes.

Examples include desmethyltramadol and desmethylsertraline.