English
Etymology
light + year
Noun
light year
- (astronomy) A unit of length (abbreviation ly) equal to the distance light travels in one year; used to measure extremely large distances.
- (in plural light years; figurative, informal) A very long way.
- The marathon runner in the lead is light years ahead of the one at the back.
- (in plural light years; figurative, informal, non-standard) A very long time.
- Some of Leonardo da Vinci's inventions were light years ahead of their time.
Usage note
- The light year is a unit of length, but because it contains the word year is sometimes assumed to be a unit of time. Its use in the figurative sense of "a very long time" is non-standard; it is preferrable to use an alternative term in this case.
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