支し川せんMeanings1nountributary; branch streamA smaller stream or river that flows into a larger one. Often used in geographical or hydrological contexts. Compare with 支流, which is more common.See also: 支流この支し川せんは本ほん流りゅうに合ごう流りゅうする前まえにいくつかの小ちいさな滝たきを形けい成せいしている。This tributary forms several small waterfalls before joining the main stream.