nLab
causal locality

A basic characteristic of physics in the context of special relativity and general relativity is that causal influences on a Lorentzian manifold spacetime propagate in timelike or lightlike directions but not spacelike.

The fact that any two spacelike-separated regions of spacetime thus behave like independent subsystems is called causal locality or Einstein causality.

(One sometimes sees a further criterion to causality, that the causal influences in timelike and lightlike directions only propagate into the future, but this is not so simply dealt with; it probably only makes sense as a statement about coarse-grained entropy in statistical physics.)

For a formalization of this idea see for instance

• local net of observables.