Final answer:
Longitude is a measurement of the east-west location on the Earth and is represented by lines of constant longitude called meridians. The prime meridian in Greenwich, England, is designated as 0 degrees longitude.
Step-by-step explanation:
Longitude is a measurement of the east-west location on the Earth and is represented by lines of constant longitude called meridians. The prime meridian, which passes through the Royal Observatory in Greenwich, England, is designated as 0 degrees longitude. Meridians extend from pole to pole and help divide the Earth into Eastern and Western Hemispheres. Longitude is essential for navigation and mapping purposes.