Static definition of 1. Angle: A graph composed of two rays with a common point is called an angle, the common endpoint is called the vertex of the angle, and the two rays are called two sides of the angle.

② Dynamic definition of angle: the graph formed by light rotating from one position to another around its endpoint is called angle, the endpoint of the rotated light is called the vertex of the angle, the light at the starting position is called the beginning edge of the angle, and the light at the ending position is called the ending edge of the angle.