Definition of Brønsted acid (Brönsted acid)

1. A molecular entity capable of donating a hydron (proton) to a base, (i.e. a "hydron donor") or the corresponding chemical species. For example: H2O, H3O+, CH3CO2H, H2SO4, HSO4-, HCl, CH3OH, NH3. See also conjugate acid-base pair.