What is the figure formed by two rays sharing a common endpoint called?

In Euclidean geometry, an angle is the figure formed by two rays, called the 'sides' of the angle, sharing a common endpoint, called the 'vertex' of the angle. Angles formed by two rays lie in the plane that contains the rays.

The word 'angle' comes from the Latin word 'angulus', meaning "corner".

In geography, the location of any point on the Earth can be identified using a geographic coordinate system. This system specifies the latitude and longitude of any location in terms of angles subtended at the center of the Earth, using the equator and (usually) the Greenwich meridian as references.

In astronomy, a given point on the celestial sphere can be identified using any of several astronomical coordinate systems, where the references vary according to the particular system. Astronomers measure the angular separation of two stars by imagining two lines through the center of the Earth, each intersecting one of the stars. The angle between those lines can be measured and is the angular separation between the two stars.