light-year

[ lahyt-yeer, -yeer ]
/ ˈlaɪtˌyɪər, -ˈyɪər /

noun

Astronomy. the distance traversed by light in one mean solar year, about 5.88 trillion mi. (9.46 trillion km): used as a unit in measuring stellar distances. Abbreviation: lt-yr
light-years,
  1. a very great distance, especially in development or progress: The new computer is light-years ahead of the old one.
  2. a very long time: It's been light-years since I've seen my childhood friends.

Origin of light-year

First recorded in 1885–90

British Dictionary definitions for light year

light year

noun

a unit of distance used in astronomy, equal to the distance travelled by light in one year, i.e. 9.4607 × 10 12 kilometres or 0.3066 parsecs

Scientific definitions for light year

light-year

The distance that light travels in a vacuum in one year, equal to about 9.46 trillion km (5.88 trillion mi). Light-years are used in measuring interstellar and intergalactic distances. Compare astronomical unit parsec.

Cultural definitions for light year

light year

The distance traveled by light in a year (over five trillion miles); a unit for measuring distances outside the solar system. The star nearest to our sun, Alpha Centauri, is more than four light years away.