Amine, an organic compound derived from ammonia. In an amine molecule, at least one of the hydrogen atoms of the ammonia molecule (NH3) is replaced by an organic radical (a group of atoms that acts as a single element). In a primary amine, one of the hydrogen atoms is replaced; in a secondary amine, two; and in a tertiary amine, all three. Most amines are poisonous, and are basic rather than acidic. The most important amine is aniline, from which dyes and other chemicals are produced.