Trigonometry is a branch of mathematics that deals with the relationships between the sides and angles of triangles. It is often used to calculate unknown angles and distances in various types of problems. The term 'trigonometry' comes from the Greek words for triangle (trigonon) and measure (metron). The four-letter word for math that is related to trigonometry is 'geom', which is short for geometry. Geometry is the study of shapes, sizes, and relative positions of figures in space.