Left mound radical — the side-form of
阜, depicting a stepped hillside. The indexing radical, marking
陀 as terrain-related (originally 'slope, uneven mountain ground'). The left-
阝 family includes
阵 (formation),
险 (steep),
阳 (sunny slope) — all hill-and-rampart vocabulary. Distinct from the right-
阝 'city' radical.