Wiktionary
meth-
pre. (context organic chemistry English) (non-gloss definition: Used to denote the presence of a single axial atom when forming names of organic compounds for methyl derivatives.)
Wikipedia
Meth-
meth- is a prefix used in chemistry. It indicates that a chemical compound has been derived from methane or contains " methyl" groups.
It serves as the number 1 when counting axial atoms in forming names of organic compounds.
Category:Chemistry prefixes