Definition of: trigonometry

(trig′ə·nom′ə·trē) noun
The branch of mathematics that treats of the relations of the sides and angles of triangles and of the methods of applying these relations in the solution of problems involving triangles: widely used in navigation, surveying, etc. [<NL trigonometria <Gk. trigōnon a triangle + metron measure]
—trig·o·no·met·ric (trig′ə·nō·met′rik) or ·ri·cal adjective
—trig′o·no·met′ri·cal·ly adverb