: 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)
: 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

Recent Examples on the Web This stellar nursery is about 450 light-years away from Earth. Laura Baisas, Popular Science, 11 Apr. 2024 Something set off some unique gravitational waves from 650 million light-years away. Morgan Haefner, Quartz, 8 Apr. 2024 What turned out to be hard for Venus will only be harder for exoplanets many light-years away. Elise Cutts, WIRED, 7 Apr. 2024 The end result was a series of overlapping spheres with slightly denser shells measuring roughly a billion light-years across — the distance BAOs had time to travel before freezing. Charlie Wood, Quanta Magazine, 4 Apr. 2024 Putting down a mere 10% would set a buyer back $100,000, which is light-years away from what an average American has in savings. Sydney Lake, Fortune, 2 Apr. 2024 However, the recent team managed to catch a supernova in the act, just 22 million light-years from Earth (which is not so far as far as galaxies are concerned). Isaac Schultz / Gizmodo, Quartz, 28 Mar. 2024 Magnetic Fields The new image—published today in The Astrophysical Journal Letters—shows a magnetic field structure very similar to that of the black hole at the center of the M87 galaxy, a supergiant elliptical galaxy around 54 million light-years away in the constellation Virgo. Jamie Carter, Forbes, 27 Mar. 2024 The Swift Go 14 proved much brighter, and the Acer, Asus, and HP were light-years ahead in color coverage. PCMAG, 27 Mar. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'light-year.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

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

Dictionary Entries Near light-year

Cite this Entry

“Light-year.” Dictionary, Merriam-Webster, Accessed 25 Apr. 2024.

Kids Definition


: 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)
: a very great distance especially in progress
light-years ahead in design

More from Merriam-Webster on light-year

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