1. fall apart  [破裂；破碎；崩溃]
[构成]：fall[落下；跌倒] + apart[分开；破碎]
例句：The old chair fell apart when I sat on it. [我一坐上去，那把旧椅子就散架了。]

2. fall behind  [落后；拖欠]
[构成]：fall[落下；跌倒] + behind[在...后面]
例句：If you don't study hard, you'll fall behind. [如果你不努力学习，你就会落后。]

3. fall down  [跌倒；失败]
[构成]：fall[落下；跌倒] + down[向下]
例句：She fell down and hurt her knee. [她跌倒了，伤了膝盖。]

4. fall for  [爱上；受骗]
[构成]：fall[落下；跌倒] + for[为了；对于]
例句：He fell for her at first sight. [他对她一见钟情。]
Don't fall for his tricks. [别上他的当。]

5. fall in love  [坠入爱河；相爱]
[构成]：fall[落下；跌倒] + in[在...里] + love[爱]
例句：They fell in love with each other last year. [他们去年相爱了。]

6. fall off  [减少；跌落]
[构成]：fall[落下；跌倒] + off[离开；脱落]
例句：Sales have fallen off recently. [近来销售额下降了。]
The leaves are falling off the trees. [树叶正从树上掉落。]

7. fall on  [落到；袭击]
[构成]：fall[落下；跌倒] + on[在...上面]
例句：The responsibility fell on him. [责任落在了他身上。]
The enemy fell on the village at night. [敌人在夜间袭击了这个村庄。]

8. fall out  [争吵；脱落]
[构成]：fall[落下；跌倒] + out[出去；向外]
例句：They often fall out over small matters. [他们经常为小事争吵。]
His hair is falling out. [他的头发在脱落。]

9. fall asleep  [入睡；睡着]
[构成]：fall[落下；跌倒] + asleep[睡着的]
例句：I fell asleep quickly last night. [昨晚我很快就睡着了。]

10. fall ill  [生病]
[构成]：fall[落下；跌倒] + ill[生病的]
例句：He suddenly fell ill yesterday. [他昨天突然生病了。]

11. fall into  [落入；陷入]
[构成]：fall[落下；跌倒] + into[进入]
例句：The boy fell into the river. [那个男孩掉进了河里。]
She fell into a deep depression. [她陷入了深深的沮丧之中。]

12. fall over  [摔倒；跌倒]
[构成]：fall[落下；跌倒] + over[倒下；翻转]
例句：He fell over and broke his leg. [他摔倒了，摔断了腿。]

13. take a fall  [遭受挫折；失败]
[构成]：take[拿；取] + a[一个] + fall[跌倒；失败]
例句：He took a fall in his business. [他在生意上遭受了挫折。]

14. free fall  [自由落体]
[构成]：free[自由的] + fall[落下；跌倒]
例句：The object is in free fall. [这个物体在做自由落体运动。]

15. heavy fall  [大量下降；大雨；大雪]
[构成]：heavy[重的；大量的] + fall[落下；跌倒]
例句：There was a heavy fall of snow last night. [昨晚下了一场大雪。]

16. sudden fall  [突然下降；突然跌落]
[构成]：sudden[突然的] + fall[落下；跌倒]
例句：The stock price had a sudden fall. [股票价格突然下跌。]

17. autumn fall  [秋天的落叶]
[构成]：autumn[秋天] + fall[落下；跌倒]
例句：The autumn fall is very beautiful. [秋天的落叶很美。]

18. waterfall  [瀑布]
[构成]：water[水] + fall[落下；跌倒]
例句：We saw a magnificent waterfall on our trip. [我们在旅行中看到了一个壮观的瀑布。]

19. price fall  [价格下跌]
[构成]：price[价格] + fall[落下；跌倒]
例句：The price fall has affected our profits. [价格下跌影响了我们的利润。]

20. nightfall  [黄昏；傍晚]
[构成]：night[夜晚] + fall[落下；降临]
例句：We should arrive before nightfall. [我们应该在黄昏前到达。]