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

The Carina Nebula is located in the Carina constellation, around 20,000 light-years away from Earth. —Kenna Hughes-Castleberry, Space.com, 5 Jan. 2026

Betelgeuse is approximately 600 light-years from Earth, and is dying a slow death that someday will turn extremely violent! —Mike Lynch, Twin Cities, 4 Jan. 2026

Their analysis showed that the planet lies about 3,000 parsecs, or just under 10,000 light-years, from Earth. —Rupendra Brahambhatt, Interesting Engineering, 3 Jan. 2026

One standout target to try locating is the Orion Nebula, a nearby stellar hotspot located 1,350 light-years away and one of the easiest deep-sky objects to spot without a telescope. —Michael D'estries, Travel + Leisure, 1 Jan. 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