Longitude is defined as the distance measured in degrees __________.

Longitude is defined as the distance measured in degrees east or west of the Prime Meridian, which is an essential line of reference in the geographic coordinate system. The Prime Meridian is located at 0 degrees longitude, and as you move east, the degrees increase up to 180 degrees, while to the west, they also increase to 180 degrees. This system allows for the precise location of points on the Earth's surface and is crucial for navigation, mapping, and understanding global geography.

In contrast, the other options relate to latitude or general mapping principles rather than specifically to longitude. Latitude measures the distance north or south of the Equator, while references to the Equator and map scales do not pertain directly to how longitude is defined in the context of geography.