topple down/over, tumble down/over, fall down/over在作“倒塌，坍塌，摔倒，倒下”解时，意思基本相同，但并不能完全换用。
(1) ①topple down/over意为“倾倒，倾塌，跌倒”。
- I tried to build a house of toy bricks but it soon toppled down/over .
我试图用积木搭起一座房子，但它很快就倒塌了。 - The child, taking his first steps, toppled down/over time after time.
小孩在学走路，跌倒了一次又一次。
②topple down还可作“失败，停止”解，是非正式用语。
- His ideas of winning power quickly toppled down when he learned who his opponent was.
当得知对手是谁时，他想掌权的想法就土崩瓦解了。 - The organization toppled down when its leader died.
其领导人一死，这个组织就崩溃了。
（拓展学习：小词详解 | topple）
(2) ①tumble down/over意为“倒塌，坍塌”，常用于建筑物。
- That bridge brought into existence for less than one year suddenly tumbled down , killing more than a hundred people.
这座桥建了还不到一年就突然倒塌了，死了一百多人。 - That old building could tumble down any day now.
这座老建筑随时都有倒塌的可能。
②tumble down/over也可用于人，意思是“摔倒，滚下，掉下”，尤指快速而猛烈地跌倒。
- Babies tumble(down) when they are learning to walk.
小孩学步时容易摔倒。 - The boy tumbled down the hillside and was seriously injured.
小男孩滚下山坡，伤得不轻。
(3) fall down/over意思也为“倒塌，坍塌”，用于人，表示“摔倒，跌倒”。
- The old man fell down/over and hurt his knee.
老人跌倒在地，伤着了膝盖。 - I saw the little girl fall over/down (=tumble over/down) and hit her head.
我看到小女孩摔倒了，碰伤了头。 - When a man is drunk, he often falls over his own feet.(over为介词)
人喝醉时常因站不住脚而摔倒。
(4) trip over意为“绊倒”，其中over为介词。
- Mind you don't trip over these roots, they are difficult to see under all these leaves.
当心，别让树根绊倒了，它们隐藏在树叶下不易被看到。
(5) ①stumble over意为“磕磕绊绊地走；绊倒；跌倒”，over为介词；有时为明确起见，可与fall一起用。
- I stumbled over a stone on the road and fell.
我被路上的石头绊了一下，摔倒了。 - They sprang away, stumbling over roots and among vines in the dark, and marching toward their destination.
他们一跃而起，穿过树藤，在黑暗中跌跌撞撞地跨越树根，向目的地行进。
②单用stumble则表示“绊了一下”。
- In the dark, he stumbled , missed his step, and fell.
黑暗中他的脚被绊了一下，一失足，摔倒了。
