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

The stars of the Pleiades are about 444 light-years distant. —Jamie Carter, Forbes, 6 Jan. 2025

But for galaxies billions of light-years away, the stars appear blended together due to the distance. —Julia Jacobo, ABC News, 6 Jan. 2025

Using a technique called gravitational lensing, the team of researchers were able to make their historic stellar discovery in a distant galaxy located nearly 6.5 billion light-years from Earth. —Eric Lagatta, USA TODAY, 6 Jan. 2025

The event was relatively easy to localize, allowing it to be associated with a specific galaxy that is relatively nearby, at least in cosmological terms (about 200 million light-years away). —John Timmer, Ars Technica, 3 Jan. 2025

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