A light-year is a unit of distance used in astronomy to measure vast distances in the universe. It is defined as the distance that light travels in one year in a vacuum. Since light travels at a very high speed of approximately 299,792 kilometers per second, or about 186,282 miles per second, a light-year is equivalent to about 9.46 trillion kilometers (or about 5.88 trillion miles). Light-years are commonly used to describe the distances between stars and galaxies because of the immense size of the universe.
