n.  1.  That branch of mathematics which treats of the relations of the sides and angles of triangles, which the methods of deducing from certain given parts other required parts, and also of the general relations which exist between the trigonometrical functions of arcs or angles.  
2.  A treatise in this science.

Noun  1.  trigonometry  the mathematics of triangles and trigonometric functions Synonyms: trig 