Light-year
From Tardis Wiki, the free Doctor Who reference
A light-year is a unit of measurement used to measure interstellar distance. It is quantified as the distance that light travels in a vacuum over the course of an Earth year.
While it is a measurement of distance, not time, terms for lengths of multiple years can be used to indicate larger values; for example, ten light years could be called a light-decade, one hundred light years could be called a light-century, and so on. Conversely, shorter periods can be used, such as a light-months, light days, and so on; Earth's distance from its sun could be expressed as 8 light-minutes.
