An Etymological Dictionary of Astronomy and Astrophysics

1. Physics: That part of the boundless four dimensional continuum in which matter can be physically extended.
   
2. Astro.: That part of the Universe which lies beyond the Earth’s atmosphere and in which the density of matter is low. Also known as outer space.

Etymology (EN): M.E., from O.Fr. espace, from L. spatium “room, area, distance, stretch of time,” of unknown origin.

Etymology (PE): Fazâ, loan from Ar.