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
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Who Knew?
-
- What is a ruelle?

Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Words at Play
Ask the Editors
Word Games
Share light-year
Time Traveler for light-year
The first known use of light-year was in 1867
See more words from the same year