Terminal Side of an Angle Definition
The terminal side of an angle θ drawn in angle standard position is the side which is not the initial side. In other terms it is the ray where measurement of an angle stops. When viewing an angle as the amount of rotation about the intersection point (the vertex) needed to bring one of two intersecting lines (or line segments) into correspondence with the other, the line (or line segment) towards which the initial side is being rotated is the terminal side. The terminal side of an angle is illustrated in the diagram below.
“Terminal Side.” From Wolfram MathWorld, mathworld.wolfram.com/TerminalSide.html.