a combining form meaning “other,” used in the formation of compound words (allotrope) and in chemistry to denote the more stable of two geometric isomers.

Nearby words

  1. alliteration,
  2. alliterative,
  3. allium,
  4. allmouth,
  5. allness,
  6. allo.,
  7. alloa,
  8. alloantibody,
  9. alloantigen,
  10. allobarbital

Also (except in chemistry) especially before a vowel, all-.

Origin of allo-

< Greek, combining form of állos other; cognate with Latin alius, else Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for allo-


before a vowel all-

combining form

indicating difference, variation, or oppositionallopathy; allomorph; allophone; allonym

Word Origin for allo-

from Greek allos other, different

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 allo-


word-forming element meaning "other," from Greek allo-, comb. form of allos "other, different" (see alias (adv.)).

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for allo-



Other; different:allotransplantation.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.