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

Vega is 26 light-years away from Earth, with one light-year equaling nearly six trillion miles. —Mike Lynch, Twin Cities, 7 June 2026

The star system in question, HD 81809, lies in the constellation Hydra and is roughly 90 to 101 light-years from Earth. —Christopher McFadden, Interesting Engineering, 6 June 2026

The triple system, known as TIC 295741342, is 3,080 light-years from Earth and was found by NASA's TESS (Transiting Exoplanet Survey Satellite) mission. —Keith Cooper, Space.com, 3 June 2026

Despite being located about 60 million light-years away in the constellation Coma Berenices, M88 is a fairly bright object in the night sky. —Adam Kovac, Scientific American, 30 May 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