An<unk>  (often represented by the generic formula HA [H+A-]) is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0. That approximates the modern definition of Johannes Nicolaus Brønsted and Martin Lowry, who independently defined an<unk>  as a compound which donates a hydrogen ion (H+) to another compound (called a base). Common examples include acetic<unk>  (in vinegar) and sulfuric<unk>  (used in car batteries).<unk> /base systems are different from redox reactions in that there is no change in oxidation state.
Acid
Carbide
Amino acid
Diol
Acyl
Halide
Ionic liquid
Bite