In geography, a meridian is a line of longitude that runs from the North Pole to the South Pole and measures the east-west position of a point on the Earth's surface. The Prime Meridian, located at 0 degrees longitude, is the starting point from which all other meridians are measured.

The Prime Meridian is also knowen as the Greenwich Meridian because it runs through the town of Greenwich.

In geography, all of the points on Earth that have the same longitude

blend together to form a line called a "meridian". Every meridian is a

semi-circle on the Earth's surface that joins the north and south poles.

Every point on a meridian has the same longitude.

A Meridian or Meridian Line is an imaginary line drawn between two points. In geography these two points are an imaginary arc on the earths surface from the North to the South Poles.

In astronomy it is an imaginary circle in a perpendicular plane to those planes of the celestial equator and horizon.