much 只能修饰不可数名词；many 只能修饰可数名词复数。
many 与 much的用法区别两者都表示“许多”,但 many 修饰或代替复数可数名词,而 much 用来修饰或代替不可数名词。
How many people are there in your family?
你们家有几个人?
How much money did you spent on it?
你在这上面花了多少钱?
Many of us left early.
我们有许多人离开得很早.
Much work has been done.
许多工作都已经做了.
