The east and west distance from the Prime Meridian, measured in degrees, is referred to as "longitude." Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Points with the same longitude lie in lines running from the North Pole to the South Pole.
The Prime Meridian, which passes through Greenwich, England, is the zero-degree longitude line. Locations to the east of the Prime Meridian are expressed as degrees east longitude up to 180 degrees, and locations to the west of the Prime Meridian are expressed as degrees west longitude up to -180 degrees.
So, the correct answer to the question "The east and west distance from the prime meridian, measured in degrees is referred to as what?" is:
longitude
