A point of the horizon and a circle extending to it from the zenith; or an arc of the horizon measured clockwise between the south-point of the horizon and a vertical circle passing through the center of any object.
An azimuth is an angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and the reference vector on the reference plane is called the azimuth.
An example of an azimuth is the measurement of the position of a star in the sky. The star is the point of interest, the reference plane is the horizon or the surface of the sea, and the reference vector points to the north. The azimuth is the angle between the north point and the perpendicular projection of the star down onto the horizon.
Azimuth is usually measured in degrees (°). The concept is used in many practical applications including navigation, astronomy, mapping, mining and artillery.