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

About 65 million light-years from Earth, three galaxies don’t look quite right. — Quanta Magazine, 14 Oct. 2026

The black hole sits at the center of the galaxy NGC 1275, located around 225 light-years away, and is the brightest galaxy of the Perseus Cluster. — Robert Lea, Space.com, 12 Oct. 2026

Smart home control, routines, general queries, calendar management, and shopping are light-years ahead of pre-AI Alexa, mostly because the new Alexa understands me better. — Jennifer Pattison Tuohy, The Verge, 8 Oct. 2026

Set the scene Etéreo, Auberge Collection (which draws its name from the Spanish word for ‘ethereal’) is only a 30-minute drive from the Cancún airport, but this slice of heaven on the Riviera Maya feels light-years away from the chaos. — Condé Nast, Condé Nast Traveler, 7 Oct. 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