light-year

American  

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

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.

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light year British  

noun

1. 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

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light-year Scientific  

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 parsec

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light year Cultural  

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.

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Etymology

Origin of light-year

First recorded in 1885–90

Compare meaning

How does light-year compare to similar and commonly confused words? Explore the most common comparisons:

• astronomical unit vs. light-year

Example Sentences

High resolution images from Hubble revealed four closely packed globular clusters inside the Perseus galaxy cluster, located 300 million light-years from Earth.

From Science Daily

De said this new observation offers another clue -- and one that comes from the closest galaxy to ours, about 2.5 million light-years from Earth, meaning it was much brighter and easier to examine.

From Barron's

Researchers reviewing that archive have uncovered evidence of a rocky planet slightly larger than Earth orbiting a Sun-like star about 146 light-years away.

From Science Daily

Several hundred million light-years after the Big Bang, clouds made of hydrogen and helium cooled enough to begin collapsing under their own gravity.

From Science Daily

While observing a repeating FRB roughly 2.5 billion light-years from Earth, researchers detected a unique signal that pointed to the presence of a nearby companion star.

From Science Daily