signatory

This term carries a heavy weight of legal obligation and formality. It is almost exclusively used in the context of international diplomacy, high-level corporate contracts, or constitutional law, where the act of signing creates a binding commitment. It suggests a transition from a mere negotiator to a committed participant. As a noun, it refers to the entity itself, while as an adjective, it describes the status of the party. Because it refers to a specific legal role, it is rarely used in casual settings, such as signing a simple greeting card or a low-stakes agreement.