Noun
(chemistry) any cation derived by the addition of a proton to the hydride of any element of the nitrogen, chalcogen or halogen families
(chemistry) any organic derivative of these compounds
onium (plural onia)
(physics) the bound pair of a particle and its antiparticle
However, the production of a muon/antimuon bound state, which is an onium, has been theorized. Source: Internet
Strong acids protonate the oxygen to give "onium ions". Source: Internet
The suffix "-onium" is mostly used for bound states of a particle with its own antiparticle. Source: Internet