The word "吐故纳新" is formed by the juxtaposition of two verb-object constructions: "吐故" and "纳新". Here, "吐" (to expel) takes "故" (the old) as its object, and "纳" (to admit) takes "新" (the new) as its object, combining directly to express the simultaneous action of discarding the old and embracing the new.