Which ions are most abundant in an acid?

The hydrogen ion is the most abundant in an acid for it is a bare proton that associates with any water in the molecule, solution or reaction so the H + ions produced by an acid exist as H3O + ions.

Moreover, in t he Arrhenius theory, an acid is a substance that dissociates to produce H + ions in solution and a base as a substance that dissociates to produce OH - ions in solution. Meanwhile, in the Bronsted-Lowery theory, an acid is considered as a proton donor.