A few important terms associated with the spherical mirrors are-
1. Pole: the geometrical center of the spherical mirror is called as its pole.
2. Centre of curvature: The center of the imaginary sphere of which the mirror is a part is called as center of the curvature.
3. Principal Axis: A straight line passing through the pole and center of curvature.
4. Principal focus: That point on principal axis through which the reflected light ray pass when incident light ray was travelling parallel to the principal axis.