light-year

noun \ ˈlīt-ˌyir \

Definition of light-year

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

First Known Use of light-year

1867

in the meaning defined at sense 1

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LIGHT-YEAR Defined for English Language Learners

light-year

Definition of light-year for English Language Learners

  • : a unit of distance equal to the distance that light travels in one year (about 5.88 trillion miles or 9.46 trillion kilometers)

  • light-years —used to say that someone or something is much better or more advanced than others

  • —used to refer to a time that is or seems very far away


LIGHT-YEAR Defined for Kids

light-year

noun \ ˈlīt-ˌyir \

Definition of light-year for Students

: a unit of length in astronomy equal to the distance that light travels in one year or about 5.88 trillion miles (9.46 trillion kilometers)


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