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 of light-year

• 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

Therefore, this light-blocking object has to be closer than those stars are, located much less than 100,000 light-years away at the most. —Big Think, 26 Mar. 2026

It is found 6,500 light-years from Earth in the constellation Taurus. —Brett Tingley, Space.com, 24 Mar. 2026

Right now the Republican Party is light-years away from that, and those who cherish conservatism should say so. —Peter Wehner, The Atlantic, 23 Mar. 2026

Imagine waking up, groggy and bearded, on a space ship light-years from Earth. —Jackie Flynn Mogensen, Scientific American, 22 Mar. 2026

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