The word 同盟 is formed from two characters: 同, meaning "same" or "together", is composed of 冂 (enclosure) and 口 (mouth), indicating collective agreement; 盟, meaning "alliance" or "oath", combines 明 (bright) and 皿 (vessel), historically referencing a ritual oath. Together, they semantically create the concept of a joint alliance where parties unite under a shared pact.