Space time and Space-time continuum

Space-time continuum and space time are semantically related. In some cases you can use "Space-time continuum" instead a noun phrase "Space time".

Space-time continuum noun - The four-dimensional coordinate system (3 dimensions of space and 1 of time) in which physical events are located.

Space time and space-time continuum are semantically related. Sometimes you can replace phrase "Space time" with "Space-time continuum", this phrases are similar.