A light-year is the distance that light travels in one year through a vacuum. Light moves at a speed of about 186,000 miles per second (300,000 kilometers per second), and over the course of one year (365.25 days), this adds up to approximately 5.88 trillion miles or about 9.46 trillion kilometers (9.46 × 10¹² km)

. To put it numerically:

• 1 light-year ≈ 9.46 trillion kilometers (9.46 × 10¹² km)
• 1 light-year ≈ 5.88 trillion miles

This unit is used primarily in astronomy to measure vast distances, such as those between stars and galaxies, where conventional units like miles or kilometers become impractical

. In summary, a light-year is a measure of distance, not time, representing how far light travels in one Earth year.