The monohalomethanes are organic compounds in which a hydrogen atom in methane is replaced by a halogen.
The four common[a] members are fluoromethane, chloromethane, bromomethane and iodomethane.
Historical name for this group is methyl halides; it's still widely used.
The compounds of this class are often described as CH3X or MeX (X - any halogen, Me - methyl group).
There are analogs with more than one hydrogen atom in methane is replaced by a halogen: Analogs with carbon atom replaced with a heavier group 14 element are also known: