light-year

noun

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 villageSuzanne Patterson

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 bubble-like form of the Garlic Nebula lies within the Milky Way some 9,132 light-years from Earth in the constellation Cassiopeia. Anthony Wood, Space.com, 24 Oct. 2025 Located about 162 light-years away from Earth, β CMi is encompassed by a disk of hydrogen moving incredibly fast. Andrew Paul, Popular Science, 22 Oct. 2025 However, while real stars are massive, glowing balls of gas located light-years away from Earth, meteors are usually just tiny bits of rock or dust—often no bigger than a grain of sand—that come from comets or asteroids. Hannah Parry, MSNBC Newsweek, 21 Oct. 2025 That fuzzy little patch is our Milky Way Galaxy’s next-door neighbor, over 2 million light-years away, with just one light year equaling almost 6 trillion miles. Mike Lynch, Twin Cities, 19 Oct. 2025 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

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Cite this Entry

“Light-year.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/light-year. Accessed 28 Oct. 2025.

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

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