谷 draws a valley as if seen from a distance: two mountain slopes flaring outward, narrowing down into a mouth-shaped opening where the water finally breaks free. Because valleys were also where the earliest farmers planted their crops, 谷 was later borrowed to write "grain" too — valley and grain now share one character and one sound, gǔ.
A piece of culture
The five grains Classical China counted its staple crops as the "five grains" (五谷) — the harvest that fed the empire. A bountiful year was wished for with the New Year blessing 五谷丰登, "may the five grains ripen abundantly." That same 谷 also names real valleys today, including 硅谷 — "silicon valley" — the Chinese name borrowed straight from California's tech hub.
Use it in a real word
山谷
shāngǔ · saan1 guk1
valley — literally "mountain valley"; you already know 山