-ium

American  

1. 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 ).

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-ium British  

suffix

1. indicating a metallic element

   platinum

   barium

2. (in chemistry) indicating groups forming positive ions

   ammonium chloride

   hydroxonium ion

3. indicating a biological structure

   syncytium

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Etymology

Origin of -ium

< New Latin, Latin, neuter suffix

Example Sentences

These regularly end in -is in the Nominative Singular, and always have -ium in the Genitive Plural.

From New Latin Grammar by Bennett, Charles E. (Charles Edwin)

Nom. sedīlia animālia calcāria -ia Gen. sedīlium animālium calcārium -ium Dat. sedīlibus animālibus calcāribus -ibus Acc. sedīlia animālia calcāria -ia Voc. sedīlia animālia calcāria -ia Abl. sedīlibus animālibus calcāribus -ibus 1.

From New Latin Grammar by Bennett, Charles E. (Charles Edwin)

In poetry, adjectives and participles in -ns sometimes form the Gen. Plu. in -um instead of -ium; as, venientum, of those coming.

From New Latin Grammar by Bennett, Charles E. (Charles Edwin)

Accent, 6; —— in gen. of nouns in -ius and -ium, 25, 1 and 2. accidit ut, 297, 2. accidit quod, 299, 1, b.

From New Latin Grammar by Bennett, Charles E. (Charles Edwin)

They always have -ī in the Ablative Singular, -ia in the Nominative, Accusative, and Vocative Plural, and -ium in the Genitive Plural, thus holding more steadfastly to the i-character than do Masculine and Feminine ĭ-Stems.

From New Latin Grammar by Bennett, Charles E. (Charles Edwin)