Meridians are imaginary lines that run from the North Pole to the South Pole on the Earth's surface. They help us measure longitude, which is the distance east or west of the Prime Meridian, located in Greenwich, England. Each meridian is marked in degrees, with the Prime Meridian at 0 degrees and the International Date Line at 180 degrees. In addition to geography, the term "meridian" is also used in traditional Chinese medicine to describe pathways in the body through which qi (or life energy) flows. These meridians are believed to connect various organs and systems, playing a crucial role in maintaining health and balance.