noun
treaty power; treaty signatory
Refers to a country that is a party to a treaty, often used in diplomatic or historical contexts.
その条約国は新たな協定に署名した。
The treaty power signed a new agreement.
複数の条約国が会議に参加した。
Several treaty signatories participated in the conference.
Compound of 条約 (treaty) + 国 (country). The exact historical derivation is uncertain, but the term is conventionally associated with international law.