1Forming nouns adopted unchanged from Latin (such as alluvium) or based on Latin or Greek words (such as euphonium)
2Forming names of metallic elements.‘cadmium’‘magnesium’
3Denoting a region of the body.‘pericardium’
4Denoting a biological structure.‘mycelium’
Modern Latin in -ium, -ium, and -ium via Latin from Greek -ion.