What does longitude measure in geographic terms?

Longitude measures the position of a point on Earth in relation to the prime meridian, which runs from the North Pole to the South Pole. It is indeed referred to as the "X coordinate" in the geographic coordinate system, where latitude represents the "Y coordinate." Longitude values are expressed in degrees east or west of the prime meridian, indicating how far a location is from this reference line.

Understanding longitude is crucial in navigation and mapping, as it helps determine a location's exact position in conjunction with latitude, which measures the distance north or south of the equator. This coordinate system allows for precise identification of locations on Earth’s surface, enabling everything from simple navigation to complex geographic data analyses.