involving three parties or elements; "the triangular mother-father-child relationship"; "a trilateral agreement"; "a tripartite treaty"; "a tripartite division"; "a three-way playoff"
You can use tripartite to describe something that has three parts or that involves three groups of people. tripartite meetings between Government ministers, trades union leaders and industrialists. involving three parts, groups etc tripartite agreement/talks etc (tripartitus, from tri- + partitus )