The valley radical. The Shuowen reads 谷 as the partial water flowing from a mountain mouth — top strokes for the half-emerging stream, 口 below for the valley opening. Indexes a small group: 豁 (open valley/clear), 欲 (desire — phonetic borrow), 豃 (gully). The 'grain' sense (谷子, 稻谷) shares the same simplified form but is historically a separate character (穀).