Which lines are used to measure longitude?

Longitude is measured using meridians, which are the lines that run from the North Pole to the South Pole. Each meridian represents a specific angular distance east or west of the Prime Meridian, which is designated at 0 degrees longitude. These lines help define time zones and assist in navigation by allowing one to determine their position in relation to the Earth’s rotational division.

Parallels, on the other hand, refer to lines of latitude that run parallel to the equator and measure distances north or south from it. The equator itself is the primary parallel at 0 degrees latitude, used to signify the dividing line between the Northern and Southern Hemispheres. Circles are a more generic term and do not specifically refer to the established lines of longitude or latitude. Thus, the use of meridians for measuring longitude is the correct association.