The word 合作 is formed by combining two independent characters, each contributing its core meaning to create a new, unified concept. The first character, 合 (hé), carries the fundamental idea of "joining", "closing", or "combining". The second, 作 (zuò), fundamentally means "to make", "to do", or "to act". When fused, they create a conceptual blend where "joining together" and "acting" merge to express the integrated idea of "cooperative action" or "working jointly".