上限 (shàngxiàn) is a noun meaning 'upper limit, cap, ceiling' — the maximum allowed value in a system, rule, or range. It is more formal and concrete than 限度 (xiàndù, 'limit, limitation'), which is broader and can be abstract. Unlike 极限 (jíxiàn, 'extreme boundary') which suggests the absolute physical or theoretical endpoint, 上限 is about a set or permitted maximum.