Is an arc of the equator, or any parallel of latitude, contained between the meridian of a place and that of Greenwich, or any other first meridian. These arcs being similar, are expressed by the same number of degrees and miles, though the absolute distance on the earth's surface decreases as the latitude increases, for which see DEPARTURE.
East longitude extends 180 degrees to the right, when looking north, and west longitude as many to the left of the first meridian.