The word "缔约国" is formed from three characters: 缔 (to conclude), 约 (treaty), and 国 (country). The combination of 缔 and 约 creates the verb-object phrase "缔约", meaning "to conclude a treaty". This phrase then modifies 国, resulting in a compound noun that literally means "treaty-concluding country", referring specifically to a contracting state or signatory nation.