both是两者都，all是三者及三者以上都。例如，You can take both of them。All the books are useful to us。
both、all有何区别
all全、都（三者以上），既可修饰可数名词也可修饰不可数名词。
All the books are useful to us.
All knowledge comes from practice.
all与否定词not连用为“部分否定”，表示“不是所有的……都……”
I don't know all of them. 他们当中我并不都认识。
All don't agree with you.=Not all agree with you. 并非所有人都同意你。
both两者都
You can take both of them.两个你都可以拿去。
与否定词连用表示“部分否定”。
I don't know both of them.他俩我并非都认识。
both...and...双方都……
He can both sing and dance.他能歌善舞。
both和all词义辨析
1、both 只能与复数的可数名词连用，与可数名词的复数形式连用时,both则指两个。
You were both a prey to compulsions.你俩都太冲动了。
2、all可与可数名词的单、复数或不可数名词连用，与可数名词的复数形式连用时, all指三个或三个以上。如：
All children deserve encouragement.所有的孩子都应得到鼓励。
both和all词语搭配
1、both
1）both of them 他们俩都…
2）both and 两个都；既...又...
3）both the two 两者；并
2、all
1）at all （否定句）根本；究竟
2）after all 毕竟；终究
3）above all 首先；尤其是
