1. fall down 跌倒,倒塌.例句：She fell down at school today. 她今天在学校摔了一跤.
2. fall over 倒在…上,fall over each other 争夺、 竞争、争先恐后.
3. fall off 从…上掉下来.例句：He fell off the bike. 他从自行车上摔了下来.