Oxonium has the following meanings:

• An oxonium ion is a positive oxygen cation, which has three bonds. For example, the protonation of a carbonyl gives an oxonium ion, with two bonds to a carbon atom and one bond to a hydrogen atom.
• The term oxonium is also used specifically to mean the hydroxonium (common name: hydronium) ion, which is the above type of oxonium, with three hydrogens (H₃O⁺).

• Oxonium (often abbreviated to Oxon) is sometimes used in university circles as a Latin name for Oxford (University) in England.

Acids | Cations