1. a prefix occurring in loanwords from Greek, having the same function as co- (synthesis; synoptic); used, with the meaning “with,” “together,” in the formation of compound words (synsepalous) or “synthetic” in such compounds (syngas).
Also sy-, syl-, sym-, sys-.

Origin of syn-

< Greek, combining form representing sýn with, together with Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for syn-


  1. with or togethersynecology
  2. fusionsyngamy

Word Origin for syn-

from Greek sun together, with
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 syn-

word-forming element meaning "together with," from Greek syn "with, together with," of unknown origin.

Online Etymology Dictionary, © 2010 Douglas Harper

syn- in Medicine


  1. Together; with:synclonus.
  2. United:syncephaly.
  3. Same; similar:synteny.
  4. At the same time:synesthesia.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.