both, all both指“两者都”，all指三个或三个以上“所有的”，可以修饰名词，也可以作代词用。

　　【例如】

　　Both sides approve of your proposal, therefore we can carry it out.

　　All work and no play makes Jack a dull boy.

　　Both of them are excellent. I really don't know whom to choose.

　　That is all I can do and all I want to say.