noun
A political principle or policy of conducting affairs between two nations directly, as opposed to multilateral approaches.
二国間主義に基づいて貿易協定を結んだ。
They concluded a trade agreement based on bilateralism.
Multilateralism, involving three or more nations, as opposed to the two-nation focus of 二国間主義.
Compound of 二国 (two countries), 間 (between), and 主義 (principle/doctrine).