Angles can exist anywhere in the coordinate plane where two rays share a common vertex. If this vertex is at the origin of the plane and the initial side lies along the positive $x$-axis, then the angle is said to be in standard position. Some angles in standard position are shown below.

Angles in standard position can be classified according to the quadrant contains their terminal sides. For example, an angle whose terminal side lies in the first quadrant is called a first quadrant angle. If the terminal side of an angle lies along one of the axes, then that angle doesn't lie in one specific quadrant; it lies along the border of two quadrants. Such angles are called a quadrantal angle.