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light year

From Wiktionary, the free dictionary
See also: lightyear and light-year

English

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English Wikipedia has an article on:
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Alternative forms

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Pronunciation

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Noun

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light year (plural light years, abbreviation ly)

  2. (astronomy) A unit of length used to measure extremely large distances, equal to approximately 9.46 trillion kilometres 10 trillion kilometres (1016 metres), equivalent to the distance light travels in one Julian year.
    • 2012 January, Robert L. Dorit, “Rereading Darwin”, in American Scientist‎[1], volume 100, number 1, archived from the original on 14 November 2012, retrieved 11 May 2013-05-11, page 23:
      We live our lives in three dimensions for our threescore and ten allotted years. Yet every branch of contemporary science, from statistics to cosmology, alludes to processes that operate on scales outside of human experience: the millisecond and the nanometer, the eon and the light-year.
  3. (chiefly in the plural, informal, figurative) A very long way.
    The marathon runner in the lead is light years ahead of the one at the back.
    • 2024 May 10, Hannah Oh, Daisy Maldonado, “50 College Graduation Gifts That Say, “I’m So Effing Proud of You!””, in Cosmopolitan‎[2]:
      Now that they've graduated, they'll have to make some mature decisions in their future. One of which? Settling on their signature scent that is lightyears away from the $10 body spray they had throughout school.
  4. (chiefly in the plural, informal, figurative) A very long time.
    Some of Leonardo da Vinci’s inventions were light years ahead of their time.

Usage notes

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  • The light year is a unit of length, but because it contains the word year, it is sometimes assumed to be a unit of time.
  • Light year and light-year are similarly common overall, lightyear being far less common.[1][2] The form hyphenated form (light-year) leads in the American corpus while the spaced one (light year) leads in the British corpus.[1][2] The Merriam-Webster Dictionary[3] and GPO Style Manual[4] favor light-year; the OED has light year.[5]

Derived terms

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Translations

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See also

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References

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  1. ↑ 1.0 1.1 “light year, light-year, lightyear”, in Google Books Ngram Viewer.
  2. ↑ 2.0 2.1 “light years, light-years, lightyears”, in Google Books Ngram Viewer.
  3. ^ “light-year”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
  4. ^ 6. Compounding Rules in U.S. Government Printing Office Style Manual, govinfo.gov
  5. ^ “light year”, in OED Online Paid subscription required⁠, Oxford: Oxford University Press, launched 2000.

Further reading

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