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

Betelgeuse’s reddish tint can be spotted gleaming from the Orion constellation, situated about 650 light-years away from Earth. —Ashley Strickland, CNN Money, 20 Jan. 2026

Some 350 light-years away, the V1298 Tau system features an infant sun-like star, just 23 million years old, orbited by four planets on compact orbits close to their star, and all of which are seen to transit. —Keith Cooper, Space.com, 20 Jan. 2026

What seems light-years away is just around the corner. —Jennifer Weil, Footwear News, 20 Jan. 2026

The beehive is one of the closest clusters to Earth (approximately 600 light-years away) and one of the youngest (around 600 to 700 million years old). —Michele Laufik, Martha Stewart, 13 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