a suffix found on nouns borrowed from Latin, especially derivatives of verbs (odium; tedium; colloquium; delirium), deverbal compounds with the initial element denoting the object of the verb (nasturtium), other types of compounds (equilibrium; millennium), and derivatives of personal nouns, often denoting the associated status or office (collegium; consortium; magisterium); -ium also occurs in scientific coinages on a Latin model, as in names of metallic elements (barium; titanium) and as a Latinization of Gk -ion (pericardium).
Origin of -ium
< New Latin, Latin, neuter suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
suffix forming nouns
indicating a metallic elementplatinum; barium
(in chemistry) indicating groups forming positive ionsammonium chloride; hydroxonium ion
indicating a biological structuresyncytium
Word Origin for -ium
New Latin, from Latin, from Greek -ion, diminutive suffix
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
Chemical element or group:californium.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.