light-year

noun

ˈlīt-ˌyir 

1

: a unit of length in astronomy equal to the distance that light travels in one year in a vacuum or about 5.88 trillion miles (9.46 trillion kilometers)

2

: an extremely large measure of comparison (as of distance, time, or quality)

seems like light-years ago

has light-years more talent

two minutes and yet light-years away from the crowded village

—Suzanne Patterson

Synonyms

• galaxy
• world

Examples of light-year in a Sentence

my sister and I are close in age, but personality-wise, there are light-years between us

Recent Examples on the Web

More than nine light-years long and 7,000 light-years distant from Earth, this image of the nebula has been refreshed with the use of new processing techniques and released as part of ESA/Hubble’s 35th-anniversary celebrations. —Alan Taylor, The Atlantic, 28 Apr. 2025

This wreckage has a ring-like structure that is around 26 light-years in diameter — that's wide enough to fit the entire solar system across it about nine times! —Robert Lea, Space.com, 25 Apr. 2025

Also known as the Southern Pinwheel, M83 is 15 million light-years away from Earth and was discovered back in 1752. —Thomas G. Moukawsher, MSNBC Newsweek, 25 Apr. 2025

What’s your reaction to the news of potential signs of life on a massive planet light-years away? —Jeremy Engle, New York Times, 25 Apr. 2025

Word History

First Known Use

1864, in the meaning defined at sense 1

Rhymes for light-year

• atmosphere
• biosphere
• centromere
• chemosphere
• chromosphere
• hemisphere
• hydrosphere
• lithosphere
• mesosphere
• microsphere
• miserere
• mountaineer

Kids Definition

light-year

noun

ˈlīt-ˌyi(ə)r

1

: a unit of length in astronomy equal to the distance that light travels in one year or 5,880,000,000,000 miles (9,460,000,000,000 kilometers)

2

: a very great distance especially in progress

light-years ahead in design