Three parallel flowing strokes. If 山 is three peaks, 川 is three streams. The earliest oracle bone forms were curvier, capturing the motion of water itself; later scribes straightened the curves into the three vertical lines you see today. Identical across 繁體 / 新字体 / 简体.

The character sits inside a small family of CJK water-words ranked roughly by size: 川 (small stream), 河 (river — most general), 江 (large river — historically the Yangtze specifically), 海 (sea). Native speakers feel the size difference even though English collapses everything to "river".

Mandarin: chuān, level 1st tone. The province 四川 (Sìchuān, "four rivers") is named for its four major waterways draining the basin. The idiom 川流不息 (chuānliú bùxī, "flowing without stopping") describes ceaseless traffic — picture continuous rush-hour cars as a river.

Japanese: on-reading セン (sen) appears in 河川 (kasen, rivers/waterways). The kun-reading かわ (kawa) is far more common — and is one of the most frequent components in Japanese surnames: 川田 (Kawada), 川上 (Kawakami, "upriver"), 川下 (Kawashimo, "downriver"), 中川 (Nakagawa, "middle of the river"), 小川 (Ogawa, "small stream").

Memory aid: three straight vertical strokes. Peaks for 山, streams for 川.