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Lunar distance (LD), also called Earth–Moon distance, Earth–Moon characteristic distance, or distance to the Moon, is as a unit of measure in astronomy. It is the average distance from the center of Earth to the center of the Moon.
An ell (from Proto-Germanic *alinō, cognate with Latin ulna) is a unit of measurement, originally a cubit, i.e., approximating the length of a man's arm from the elbow ("elbow" means the bend or bow of the ell or arm) to the tip of the middle finger, or about 18 inches (457 mm); in later usage, any of several longer units.