# What is the definition of longitude?

Longitude is the angular distance of any point measured east or west on the Earth's surface. Meridians are vertical longitude lines, while parallels are horizontal latitude lines.

Meridians, or vertical longitude lines, converge at the poles and are widest at the equator. Greenwich, England is known as the Prime Meridian. It serves as a reference point for other longitudes and is designated as zero degrees. Longitude values are expressed in degrees, and the degrees are divided into minutes and seconds. Longitude values indicate the angular distance between Greenwich and points east or west of it on the surface of the Earth.

Reference:
Q&A Related to "What is the definition of longitude?"
 Longitude:1:the angular distance between a point on any meridian and the http://www.chacha.com/question/what-is-a-short-def...
 line of longitude: an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator http://www.kgbanswers.com/whats-the-definition-of-...
 Latitude and Longitude. Lines of latitude and longitude are imaginary lines that form a grid covering the whole globe. This grid helps geographers find the location of places anywhere http://www.quora.com/Geographic-Coordinate-System/...
 They are imaginary lines running north to south from the poles on Earth, e.g. the Prime Meridian. It can also be used to locate a place on a map. Think of the Pirate remark that,& http://wiki.answers.com/Q/What+is+the+longitude+of...