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

Peering light-years into the distance also puts my earthly concerns into perspective.

From The Wall Street Journal

A new study led by Yongda Zhu at the University of Arizona suggests these black holes can also slow the formation of stars in galaxies located millions of light-years away.

From Science Daily

Later, Webb observations showed the galaxy lies about 8 billion light-years away, meaning the explosion occurred long before Earth formed.

From Science Daily

The Crab Pulsar sits at the center of the Crab Nebula in the Perseus Arm of the Milky Way, about 6,500 light-years from Earth.

From Science Daily

Some of the most intriguing targets include the TRAPPIST-1 system planets d, e, f, and g, located about 40 light-years from Earth, as well as LHS 1140 b, which lies 48 light-years away.

From Science Daily