ETYM Greek, both.
Of both kinds; Chemistry, reacting as either alkali or acid.
Term used to describe the ability of some chemical compounds to behave either as an acid or as a base depending on their environment. For example, the metals aluminum and zinc, and their oxides and hydroxides, act as bases in acidic solutions and as acids in alkaline solutions.
Amino acids and proteins are also amphoteric, as they contain both a basic (amino, –NH2) and an acidic (carboxyl, –COOH) group.
(Chemistry) Having characteristics of both an acid and a base and capable of reacting as either; SYN. amphiprotic.