light-year

American  

[lahyt-yeer, -yeer] / ˈlaɪtˌyɪər, -ˈyɪər /

noun

1. Astronomy. the distance traversed by light in one mean solar year, about 5.88 trillion mi. (9.46 trillion km): used as a unit in measuring stellar distances. lt-yr

2. light-years,

   1. a very great distance, especially in development or progress.

      The new computer is light-years ahead of the old one.

   2. a very long time.

      It's been light-years since I've seen my childhood friends.

---

light year British  

noun

1. a unit of distance used in astronomy, equal to the distance travelled by light in one year, i.e. 9.4607 × 10 ¹² kilometres or 0.3066 parsecs

---

light-year Scientific  

1. The distance that light travels in a vacuum in one year, equal to about 9.46 trillion km (5.88 trillion mi). Light-years are used in measuring interstellar and intergalactic distances.

2. Compare astronomical unit parsec

---

light year Cultural  

1. The distance traveled by light in a year (over five trillion miles); a unit for measuring distances outside the solar system. The star nearest to our sun, Alpha Centauri, is more than four light years away.

---

Etymology

Origin of light-year

First recorded in 1885–90

Compare meaning

How does light-year compare to similar and commonly confused words? Explore the most common comparisons:

• astronomical unit vs. light-year

Example Sentences

Inside a specially designed chamber, the researchers recreated the harsh environment found in vast clouds of cosmic dust located thousands of light-years from Earth.

From Science Daily

Betelgeuse is located about 650 light-years from Earth in the constellation Orion.

From Science Daily

This white dwarf system lies about 200 light-years from Earth in the constellation Hydra.

From Science Daily

"I'm confident that there is life out there somewhere, even if it's 100 light-years away. That's why we explore -- to see what's out there."

From Science Daily

One of the new discoveries is a planet known as HIP 54515 b, which orbits a star located 271 light-years away in the constellation Leo.

From Science Daily