(1) 在底部。如：

The bodies of the three climbers were located at the bottom of a steep gully.

在陡峭的隘谷谷底找到了3名登山者的遗体。

A tall tree stands at the bottom of the hill.

山脚下有一颗很高的树。

There’s a hole at the bottom of the flower pot. 花盆底部有个洞。

Sign your name at the bottom of the page. 请在这页的最后签上你的名字。

(2) 在远处，在尽头。如：

The hospital is at the bottom of the street. 医院在街的尽头。

We grow vegetables at the bottom of our garden. 我们在花园的尽头种蔬菜。

Our poultry are kept at the bottom of the garden. 我们的家禽养在花园的尽头。

除at the bottom of the garden外，还有at the bottom of the road / street等。如：

There’s a pub at the bottom of the road. 路的尽头有一家酒馆。

There's a shop at the bottom of the street. 这条街的尽头有家商店。

(3) 在最后；在底层。如：

Start at the bottom and try to work your way up.

从底层干起，然后努力一步步升上去。

He is at the bottom of the class. 他在班上排名最后。

He sat at the bottom of the stairs

他坐在最下面的一级楼梯上。

Ordinary workers in state industry, once favoured, suddenly found themselves at the bottom of the heap.

曾经养尊处优的国企普通工人，突然发现自己已跌至社会底层。

(4) 是……的根本原因。如：

Often I find that anger and resentment are at the bottom of the problem.

我常常发现愤怒和不满是问题的真正根源。

Carelessness is at the bottom of all great mistakes.粗心大意是一切重大错误的根源。

Wine is at the bottom of his illness. 饮酒是他生病的根本原因。

知识拓展：

on the bottom 、at the bottom和in the bottom of的区别是：

on the bottom of 底下（如杯子外侧的底部）；

at the bottom of 底端（如在书本每一页的底部）；

in the bottom of 物体本身的底部（如杯子内侧的底部）。例如：

The result was that the engine ended up at the bottom of the canal

结果引擎最终沉到了运河底。

Answers can be found at the bottom of page 8.

在第8页末尾可以找到答案。

There's an extra duvet in the bottom drawer of the cupboard.

橱柜最底层的抽屉里还有一床羽绒被。

There is some deposit in the bottom of the flask.

这只烧杯的底部有些沉淀物。

请仔细体会一下三例句：

There is some tea left in the bottom of the cup. 有些茶叶留在茶杯底部。（茶叶在杯子内侧的底部）

There is some tea left on the bottom of the cup. 有些茶叶留在茶杯底部。（茶叶在杯子外侧的底部）

There is some tea left at the bottom of the cup. 有些茶叶留在茶杯底部。（茶叶在杯子内侧和茶水之间的底部，即茶叶在杯子里的茶水里的底部）

He locked these papers up in the bottom drawer.

他把这些文件锁在底层抽屉里。

但是现在英语已经不太注重这些细微的差别，许多时候这些介词的区别并不明显：

Spread the onion slices on the bottom of the dish.

把洋葱片铺在盘底。

The sunken sailing-boat was a glimmer of white on the bottom

沉没的帆船在海底闪烁着白光。

Through the clear water, we could see fish on the bottom.

通过清澈的水，我们能看见水底的鱼。