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

• world
• galaxy

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

Leaning where evidence points, though, is important—even though how dark energy behaves can seem light-years away from everyday life on Earth. —Sarah Scoles, JSTOR Daily, 31 July 2025

For example, the BOAT was about 2.4 million light-years from Earth. —Andrew Paul, Popular Science, 30 July 2025

This blue-white binary star lies about 250 light-years away. —Jamie Carter, Forbes.com, 28 July 2025

Illustration: Getty Images A team of astronomers from the University of Montreal has discovered a new potentially habitable exoplanet orbiting the red dwarf star L 98-59, 35 light-years from Earth. —Jorge Garay, Wired News, 28 July 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