1. a combining form meaning “alone,” “single,” “one” (monogamy); specialized in some scientific terms to denote a monomolecular thickness (monolayer) and adapted in chemistry to apply to compounds containing one atom of a particular element (monohydrate).
Also especially before a vowel, mon-.

Origin of mono-

< Greek, combining form of mónos alone Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for mono-


before a vowel mon-

combining form
  1. one; singlemonochrome; monorail
  2. indicating that a chemical compound contains a single specified atom or groupmonoxide

Word Origin for mono-

from Greek monos
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for mono-

word-forming element meaning "one, alone; containing one (atom, etc.)," from Greek mono-, comb. form of monos "single, alone," from PIE root *men- "small, isolated" (cf. Greek manos "rare, sparse," Armenian manr "thin, slender, small," and perhaps English minnow).

Online Etymology Dictionary, © 2010 Douglas Harper

mono- in Medicine


  1. One; single; alone:monomorphic.
  2. Monomolecular; monatomic:monolayer.
  3. Containing one atom, molecule, or group:monomer.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

mono- in Science


  1. A prefix that means “one, only, single,” as in monochromatic, having only one color. It is often found in chemical names where it means “containing just one” of the specified atom or group, as in carbon monoxide, which is carbon attached to a single oxygen atom.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.