How can space be considered empty when it is full of space?

Answer 1

Space is just a certain volume of the universe in which there is extremely little matter. Being "full of space" is a figure of speech which is scientifically not correct. For example, 25 liters of air contains 6x10^23 molecules at room temp and 1 atm. Now, if we could provide a 1x10-23 atmospheric vacuum to that space, the number of molecules would be 6. The space hasn't changed, only the number of molecules in it.

Answer 2

Space as an absence of matter/mass only happens in a vaccuum or the hypothetical airless environment.

Answer 3

^that sounds about right yes,
-nods-