Greek for “of equal number of clauses,” isocolon is a rhetorical device that produces a sense of order by balancing parallel elements that are similar in structure and length within a sentence. An isocolon need not have three elements, but the requirement of parallel and balance means that it often takes a tripartite shape, technically called a tricolon.
Over at The Millions, Ivan Kreilkamp explains how the tricolon is used to create a powerful book title.