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Noun: light-year  'lIt,yeer
  1. The distance that light travels in a vacuum in 1 year; 5.88 trillion miles or 9.46 trillion kilometres
    "The nearest star system, Alpha Centauri, is about 4.3 light-years away";
    - light year

Derived forms: light years, light-years

Type of: astronomy unit

Encyclopedia: Light-year