- (chemistry) Compound containing both an amino and a carboxylic acid group. The --NH2 group.
- (biology) an organic acid containing the amine group (NH2) and serving as building material for proteins. Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby
- (biotechnology) Any of 20 basic building blocks of proteins--composed of a free amino (NH2) end, a free carboxyl (COOH) end, and a side group (R).