mountain和hill的区别：

mountain的意思是“山”、“山岳”，其复数形式mountains 常表示 “山脉”，通常指比hill 大或陡峭的高山，例如：It’s the highest mountain in the world（它是世界上最高的山）。hill的意思是“小山”、“丘岭”，通常指比 mountain 小的山，例如：The house stands on the top of the hill（房子位于山顶上）。

mountain柯林斯释义

1、N-COUNT 山;山岳;高山

A mountain is a very high area of land with steep sides.

2、QUANT 大量;大堆

If you talk about a mountain of something, or mountains of something, you are emphasizing that there is a large amount of it.

3、PHRASE 极大的困难;难办的事情；棘手的难题

If you say that someone has a mountain to climb, you mean that it will be difficult for them to achieve what they want to achieve.     

hill柯林斯释义                                                     

1、N-COUNT;  小山;山冈;山丘

A hill is an area of land that is higher than the land that surrounds it.

We trudged up the hill to the stadium.

我们费力地爬到山上的体育场。

2、PHRASE 人老珠黄;在走下坡路;在衰退中;过气

If you say that someone is over the hill, you are saying rudely that they are old and no longer fit, attractive, or capable of doing useful work.