fell off fell down的区别：中文意思不同、用法不同、侧重点不同。fell off意为“下降”、“掉下来”、“扫兴颓丧”、“离开”，侧重于从高处向下；fell down意为“流下”、“跌到”，侧重于直直的向下。
一、fell off的含义及用法介绍
fell off意思为下降;(从马上)掉下来;扫兴颓丧;离开。例句有：
1、The bandage gradually unwound and fell off.
绷带逐渐松开脱落了。
2、Suddenly the horse lurched to one side and the child fell off.
马突然歪向一边，小孩就摔了下来。
3、She cycled round the corner, lost her balance and fell off.
她骑车拐弯时失去平衡，摔了下来。
4、Her cap fell off in the street and blew away
她的帽子掉在大街上，被风吹走了。
5、When she said she was engaged I nearly fell off my chair.
她说她订了婚时，我几乎大吃一惊。
二、fell down的含义及用法介绍
fell down意为(向下游)流下;〔美俚〕失败;跌倒。例句有：
1、The house collapsed.; The house fell down.
房子倒塌了。
2、The old lady fell down in adoration before Buddhist images.
那老太太在佛像面前顶礼膜拜。
3、The plan fell down because it proved to be too expensive.
这项计划因费用过高而告吹。
4、Many buildings fell down during the earthquake.
在地震中许多楼房倒塌。
5、Suddenly the bottle fell down onto the floor and broke into pieces.
突然瓶子掉到地上摔成了碎片。
