Happearv on karboksüülhapperühmade (−C(=O)OH) arv keemilises ühendis, näiteks rasvhappes, või ühendite segus, ehk teisisõnu, see on aines sisalduvate vabade rasvhapete protsent keemilises ühendis.
The acid value is a measure of the number of carboxylic acid groups (−C(=O)OH) in a chemical compound, such as a fatty acid, or in a mixture of compounds. In other words, it is a measure of free fatty acids present in a substance.
