-ium +

(Greek: a suffix; scientific names; names of metallic elements; a part, lining, or enveloping tissue, region; little; representing a diminutive force)

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).

This ending of -ium also occurs in scientific terms on a Latin model; such as, in names of metallic elements (barium; titanium) and as a Latinization of Greek -ion (pericardium).