light-year

[ lahyt-yeer, -yeer ]

noun

1. 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. : lt-yr
2. 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.

light year

noun

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

light-year

1. 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.
2. Compare astronomical unit

light year

1. 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.

Word History and Origins

Origin of light-year¹

First recorded in 1885–90

Example Sentences

One magnetar is only about a light-year from the black hole at the center of the Milky Way.

From The Daily Beast

One could imagine falling forty-two thousand miles, where one couldn't imagine falling a light-year.

From Project Gutenberg

That expedition perished after less than a light-year when its hydroponics system failed.

From Project Gutenberg

But this monster—a thing now as big as the whole Solar System doubtless—was speeding through a light-year in a moment!

From Project Gutenberg

"The distance is half a light-year now, sir," reported the navigation officer.

From Project Gutenberg

In popular writings, another unit: a light-year, has for a very long time been employed.

From Project Gutenberg