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

There are other ways of seeing what things were like back then: Astronomers can point cameras directly at galaxies that are 5 billion light-years distant and capture light that left them 5 billion years ago. —Ross Andersen, The Atlantic, 5 Nov. 2024

Appearing like a pair of red eyes in the darkness of space, the two galaxies are located millions of light-years away from Earth. —Marco Rubio, Newsweek, 2 Nov. 2024

Vega: ‘Uniquely Smooth’ Disk Just 25 light-years from the solar system, Vega is 455 million years old, a tenth of the age of our sun, but 40 times brighter. —Jamie Carter, Forbes, 1 Nov. 2024

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

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