双边 (shuāng biān) is an adjective meaning 'bilateral' — involving two parties, typically used for agreements, talks, or relations between two countries. It contrasts with 多边 (duō biān, multilateral, involving many parties) and 单边 (dān biān, unilateral, one side). Unlike 双向 (shuāng xiàng, 'two-way' for communication or traffic), 双边 is reserved for formal diplomatic or economic contexts.