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

• galaxy
• world

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 Milky Way is our home galaxy with a disc of stars that spans more than 100,000 light-years. —Eric Lagatta, USA Today, 23 May 2025

Gamma Cephei is actually two stars, a binary star system located some 45 light-years from Earth in the constellation Cepheus. —Anthony Wood, Space.com, 20 May 2025

The spiral galaxy is home to Earth and hundreds of billions of stars spanning more than 100,000 light-years, NASA said. —Hannah Poukish, Sacbee.com, 19 May 2025

Spica is actually a double star system around 250 light-years, or a little over 1,400 trillion miles, away from Earth. —Mike Lynch, Twin Cities, 18 May 2025

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