bottom
单词辨析：
词义最广泛，可指各种事物的最底端部分。
Hold the bottom of the ladder for me, please!
请帮我扶住梯子下部！
Be careful! The bottom of the pool is very slippery.
小心！池底很滑。
So many fish live on the sea bottom.
生活在海底的鱼数量繁多。
指构成某物底部的一层，也指河、湖、海等的水底部分。
on the sea bed
在海底
the bed of a river
河床
All the child wants is the prawns on a bed of lettuce.
这个孩子只想吃铺在生菜上面的大虾。
The railway was built on a bed of solid rock.
铁路建在硬石地基上。
指海洋、山洞等的底，或建筑物中的地板、地面。
creatures living on the ocean floor
生活在海底的生物
the floor of a bridg
桥面
He left his books lying all over the floor.
他把书扔得满地都是。
相关例句：
She was at rock bottom. Her long-term love affair was breaking up and so was she.
她整个人跌至了谷底。她漫长的爱情要告结束了，她也要崩溃了。
The two systems are, at bottom, conceptual models
这两个系统实质上是两种概念模式。
He was found dead at the bottom of a lift shaft.
他被发现死在了电梯井的底部。
The bottom had fallen out of the city's property market.
该市的房地产市场已陷入极度低迷。
The bottom of the garden was given over to vegetable plots.
花园的尽头留作了菜地。
I'm happy, and I mean that from the bottom of my heart
我很开心，而且是那种发自肺腑的开心。