The transitive closure R* of a relATion R is defined by x R y => x R* y x R y and y R* z => x R* z I.e. elements are relATed by R* if they are relATed by R directly or through some sequence of intermediATe relATed elements. E.g. in graph theory, if R is the relATion on nodes "has an edge leading to" then the transitive closure of R is the relATion "has a pATh of zero or more edges to". See also Reflexive transitive closure.