Sentence:  General relativity <WSD>endows</WSD> spacetime with a causal structure described by observer-invariant "light cones". [...] Points "inside" a light cone are causally connected with its vertex, while points "outside" the same light cone are out-of-causal contact with its vertex. 
Meaning of the word marked with <WSD> tags:  "Followed by" '''(with)''', "or rarely by" '''(of)''': to enrich or furnish with some faculty or quality.