-ium(redirected from -um)
Also found in: Medical.
Chemical element or group: californium.
[New Latin -ium, neuter n. suff., from Greek -ion.]
suffix forming nouns
1. (Chemistry) indicating a metallic element: platinum; barium.
2. (Chemistry) (in chemistry) indicating groups forming positive ions: ammonium chloride; hydroxonium ion.
3. (Biology) indicating a biological structure: syncytium.
[New Latin, from Latin, from Greek -ion, diminutive suffix]
a suffix found on nouns borrowed from Latin, esp. 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).
[< New Latin, Latin]
a suffix of scientific coinages, occurring esp. in names of elements ( barium; titanium) and names of plant and fungus structures ( mycelium; pollinium), and in Latinizations of the Greek formative -ion (pericardium), as well as coinages modeled on such words ( epithelium; periodontium).
[< New Latin or Latin -ium (< Greek -ion)]