-ium
/ɪəm/suffix
1
- forming nouns adopted unchanged from Latin (such as alluvium) or based on Latin or Greek words (such as euphonium)［构成直接引自拉丁语（如alluvium）或基于拉丁语或希腊语的名词（如euphonium）］ 。
2
- （亦作-um）forming names of metallic elements构成金属元素的名称：
cadmium
magnesium.
3
- denoting a region of the body表示“身体的某部位”：
pericardium.
4
- denoting a biological structure表示“生物结构”：
mycelium.
词源
modern Latin in senses 2, 3, and 4, via Latin from Greek -ion.