1.fall apart 破碎，破裂
例句：But having a strong and honest kind of relationship will it fall apart.
一个坚强的和诚实的感情关系将会破碎。
2.fall asleep 入睡，长眠，死
例句：He started to fall asleep; I knew he was exhausted so I stroked his hair and watched him.
他睡着了,我知道他太累了,于是我轻轻地抚摸着他的头发,看着他。
3.fall back on 借助于,依靠，撤退到
例句：Doctors sometimes fall back on old cures.
医生们有时求助于传统疗法。
4.fall behind 落在后面
例句：They charge lower upfront fees than other cards do. But if you fall behind, it's tough.
他们比其他卡收取的预支费要低，但是如果你拖欠还款，那就日子艰难了。
5.fail to do sth 做某事失败
例句：Many people fail to do this and wonder why they cannot concentrate.
很多人做不到这一点，并想知道为什么他们不能全神贯注。
6.fall down 跌倒，摔倒，失败，未能符合要求
例句：There's nothing to be afraid of. The sky won't fall down.
没有什么好怕的， 天不会塌下来。