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

light-year Synonyms



LIGHT-YEAR Defined for English Language Learners

light-year

noun

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)


Seen and Heard

What made you want to look up light-year? Please tell us where you read or heard it (including the quote, if possible).

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

serious difficulty or misfortune

Get Word of the Day daily email!

Test Your Vocabulary

The Exceptions Quiz III

  • one-green-toy-robot-amidst-many-red-toy-robots
  • Which of these words does not mean "nonsense"?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!