Define the term "longitude".

Longitude is defined as the angular distance of a location east or west of the Prime Meridian, which is situated at zero degrees longitude. This concept is crucial for navigation and geography as it allows for the precise determination of a geographic position. Longitude is measured in degrees, with values ranging from 0 degrees at the Prime Meridian to 180 degrees east and 180 degrees west. Understanding longitude helps navigators accurately chart their course on the globe, making it an essential component in the study of navigation.

The other options do not represent the concept of longitude correctly. The first option refers to latitude, which measures degrees north or south of the equator. The second option describes distance, which does not specify angular measurement. The fourth option pertains to elevation differences, which is unrelated to the concepts of longitude or navigation.