noun suffix
1. -s
[New Latin, perhaps after such words as Latin medium ]
a.
(1) : chemical element
sod ium
uran ium
(2) : chemical radical
ammon ium
b. : an ion having a positive charge — in names of complex cations (as those derived from an organic base)
imidazol ium [C 3 H 4 N 2 H] +
pyridin ium
nitrosyl ium NO +
— compare -onium
2. plural -iums also -ia
[New Latin, from Latin, from Greek -ion (n. suffix, often of diminutive force)]
: small one : mass — especially in biological terms
onch ium
pollin ium