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

Related article Astronomers’ discovery of distant Milky Way-like galaxy challenges our theories of how cosmos evolved Euclid is designed to observe billions of galaxies that stretch 10 billion light-years away to reveal how matter may have been stretched and pulled apart by dark energy over time. —Ashley Strickland, CNN, 23 Oct. 2024

In 2022 Oei and his fellow researchers uncovered another black-hole-spewing jet system that, end-to-end, spans 16 million light-years, or 100 Milky Ways. —Saima S. Iqbal, Scientific American, 23 Oct. 2024

Both are great and light-years better than rubber bands or a Ziploc. —Jen Murphy, Outside Online, 21 Oct. 2024

And where better to test the idea than TRAPPIST-1, located just 40 light-years away? —Michael Irving, New Atlas, 21 Oct. 2024

Word History

First Known Use

1864, in the meaning defined at sense 1

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