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。
...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。