(1) 两者都可用来修饰不定代词、形容词、副词、动词、介词短语等，此时两者常可换用：

It’s almost [nearly] impossible. 那几乎是不可能的。

He almost [nearly] always arrives late. 他差不多总是迟到。

The girl nearly(almost)fainted. 这姑娘差点(几乎)晕倒了。

They have almost [nearly] run out of food. 他们的食品几乎(差不多)已经吃完了。

He went out almost [nearly] every evening. 他几乎(差不多)每天晚上都出去。

It was nearly [almost] five thirty. 几乎已经五点半了。

He fell and almost [nearly] broke his leg. 他摔了一跤，险些摔断了腿。

(2) almost 可用于 any 以及 no, none, nobody, nothing, never 等否定词之前，但 nearly 一般不这样用：

Almost any man can do it. 几乎任何人都会做。

Almost no one came to the party. 几乎没有人来参加晚会。

但是，两者都可用在否定动词之前：

He almost [nearly] didn’t catch the bus. 他差点没赶上公共汽车。

(3) nearly 前可用 very, pretty, not 等词修饰，但 almost 之前不能用这些词：

It’s not nearly so difficult as you think. 这远不像你想像的那么难。

【注】not nearly 意为“远非”, very [pretty] nearly 意为“几乎”，都是习语。

(4) 有时 almost 可表示十分相似(但又不完全相同)，此时不用 nearly：

I almost wish I’d stayed at home. 我真有点后悔没在家里呆着。