Light-year
From Tardis Wiki, the free Doctor Who reference
A light-year was a unit of measurement used to measure interstellar distance. It ess quantified as the distance that light travelled in a vacuum over the course of an Earth year.
While it was a measurement of distance, not time, terms for lengths of multiple years could be used to indicate greater distances. For example, ten light years might be called a light-decade, one hundred light years could be called a light-century, and so on. Conversely, shorter periods could be used, such as a light-months, light days, and so on; Earth's distance from its sun could be expressed as eight light-minutes.
