Longitudes

Part of speech: noun

Definitions

1. A system of measurement that determines the east-west position of a point on the Earth's surface based on the angle from a prime meridian
2. The geographical coordinates measured in degrees that indicate how far a location is from the reference line of longitude
3. A set of lines running from the North Pole to the South Pole that provide a framework for mapmaking and navigation

Etymology: The Latin "longitudo" meant "length" or "extent," built from "longus," meaning "long." Its partner "latitude" comes from "latus," meaning "wide," so the pair originally described length and breadth. Only later were these Latin words applied to positions on the globe. Strictly speaking, the word names the angle rather than the line. The pole-to-pole lines in the definition are meridians, and a longitude is how far east or west a place lies from a chosen reference meridian, measured in degrees. The lines run north and south, but the measurement is east and west, which is why the term can seem backwards at first.