周zhōu

週 (zhōu, "week") narrows the meaning of 周 to a cycle of seven days — the traditional form preserves what simplified Chinese merged back into the older character. 周 itself is ancient, a pictograph of fields planted in a ring, the surrounding growth eventually suggesting "all" and "circumference." It survives as one of China's most common surnames, and in the Zhou dynasty, where the character was first written.