Distance in degrees east or west of the prime meridian at 0В° measured by the angle between the plane of the prime meridian and that of the meridian through the point in question, or by the corresponding time difference.
an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; "all points on the same meridian have the same longitude"
the angular distance between a point on any meridian and the prime meridian at Greenwich
