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

Unsurprisingly, Google's remedy position is light-years away from the Justice Department's. —Ryan Whitwam, Ars Technica, 10 Mar. 2025

Alpha Centauri is the closest star system to our own, lying around 4.3 light-years away. —Robert Lea, Space.com, 5 Mar. 2025

The Tucana-Horologium cluster was about 228 light-years from our solar system at the time, while Upper Centaurus Lupus was about 457 light-years away. —Michael Irving, New Atlas, 2 Mar. 2025

The third category only gets out to four light-years, which isn’t even as far as the closest star to the sun. —Phil Plait, Scientific American, 27 Feb. 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