onium

In chem., a termination given to the names of compound radicals which are analogous in structure and chemical function to ammonium, NH4, as phosphonium, PH4, or tetramethylphosphonium, P (CH3)4.

Any cation derived by the addition of a proton to the hydride of any element of the nitrogen, chalcogen or halogen families.

Any organic derivative of these compounds.

The bound pair of a particle and its antiparticle.