▪ I. -on, suffix1
[f. the ending of ion (and anion, cation).]
1. Physics. a. Used (first in electron2) to form the names of sub-atomic particles, as hyperon, meson, neutron, proton.
The example of electron gave rise to a few particle names in -tron, q.v.; but proton, chronologically the second word of this group, has proved the dominant model.
b. Used to form the names of quanta, as graviton, phonon.
2. Used, esp. in molecular biology, to form the names of some entities conceived of as units, as codon, muton, operon, pedon.
▪ II. -on, suffix2
[f. Gr. -ον, neut. of -ος, nom. masc. sing. ending of many adjs.]
The ending of the names of the noble gases other than helium, as argon (the earliest named), radon.