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

Its host star is a dim bulb of a red dwarf about 49 light-years from our sun. — Phil Plait, Scientific American, 21 Aug. 2026

The Hubble Space Telescope captured this twinkling image of NGC 6723, or the Chandelier Cluster, a globular star cluster located 27,000 light-years away in our Milky Way galaxy. — Chelsea Gohd, Space.com, 21 Aug. 2026

Millions of light-years away, but because of that black thing Brit had come riding up the hill at dusk. — Literary Hub, 19 Aug. 2026

The enormous columns of gas and dust sit inside the Eagle Nebula, about 6,500 light-years away, and stretch roughly five light-years. — Kaif Shaikh, Interesting Engineering, 15 Aug. 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