mono- Syllabification: (mono-) (also mon- before a vowel)Definition of mono- combining form 1one; alone; single:monorail with an extreme, singular character to the point of dominance or exclusion:monolithic monomania monopoly 2 Chemistry (forming names of compounds) containing one atom or group of a specified kind:monoamineOrigin:from Greek monos 'alone'mono- in other Oxford dictionaries Definition of mono- in the British & World English dictionary