Mon- \Mon-\ Same as {Mono-}. Mono- \Mon"o-\, Mon- \Mon-\ [Gr. ?.] A prefix signifying one, single, alone; as, monocarp, monopoly; (Chem.) indicating that a compound contains one atom, radical, or group of that to the name of which it is united; as, monoxide, monosulphide, monatomic, etc.