light-year

noun

ˈlīt-ˌyir How to pronounce light-year (audio)
Synonyms of light-yearnext
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

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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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The exoplanet orbits the star HD 176071 located around 335 light-years away, and is about two and a half times the size of Earth, but has about eight and a half times the mass of our planet. — Robert Lea, Space.com, 26 Aug. 2026 The park feels light-years away from the closest major airport, Midland (235 miles away), and this seclusion ensures the park’s night views stay dazzling. — Stephanie Vermillion, Travel + Leisure, 23 Aug. 2026 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 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 See All Example Sentences for light-year

Word History

First Known Use

1864, in the meaning defined at sense 1

Time Traveler
The first known use of light-year was in 1864

Rhymes for light-year

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Browse Nearby Words

lightwood
light-year
light-years ahead
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Cite this Entry

“Light-year.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/light-year. Accessed 1 Sep. 2026.

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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

More from Merriam-Webster on light-year

Britannica.com: Encyclopedia article about light-year

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