The word "赞成" is formed through the classical Chinese method of logical semantic compounding, where two independent characters, each with their own meaning, are combined to create a new, more specific concept. The first character, "赞" (zàn), carries the core meaning of "to support" or "to assist". The second character, "成" (chéng), means "to accomplish" or "to become". Their combination does not follow a grammatical rule but a conceptual fusion, essentially meaning "to support (something) into accomplishment". Thus, the compound naturally expresses the idea of "to approve" or "to agree with", as it conceptually frames agreement as an act of supporting a proposition or plan to the point of its fulfillment.