break up v. 打碎, 破碎, 分裂, 结束, 衰落, 分解, 变坏, 驱散
侧重于物理上的分解,同时有精神崩溃、终止、结束、解散的含义
break down v. 毁掉, 制服, 压倒, 停顿, 倒塌, 中止, 垮掉, 分解
侧重于化学上的分解,同时还有镇压、机器损坏故障、健康状况下降、计划终止等
例句:The ice began to break up on the river.
Tom broke down the motor bike which he bought five years ago.