much,a number of,the number of,a great deal of.四者有什么区别并且在句子中

a number of 和a great deal of 在意思上相同,但用法不一样.a number of 后面只能跟可数名词的复数形式,而a great deal of 后面只能跟不可数名词.
例如：A number of accidents always occur on rainy days.雨天常常有许多事故发生.
A number of books are missing from the library.图书馆的一些书不见了.
I spent a great deal of my time on this work.我在这项工作上花了不少时间.
另外,a great deal of 也可说成a good deal of.
例如：She spends a good deal of money on clothes every year.她每年在衣服上花了不少钱.
除了 a number of 之外,也可以用a large/good number of 或(large) numbers of 来表示数量众多,意思为“大量的,众多的”
例如：Numbers of people came from all parts of the country to see the exhibition.
许多人从国内来参观这个展览.
需要引起注意的是,若用the number of ,后面仍需用名词复数,但谓语动词则应用单数.因为这时表示的是数字,而非数量.
例如：The number of books missing from the library is very large.
图书馆遗失的图书数量很大.
MUCH 同 a great deal of,但是可以做疑问句,
比如HOW MUCH,或者在比较级前面
如：MUCH BETTER,表示好的多
the number of 表示,的数量,和前面的几个的意思完全不沾边

much = a great deal of 修饰不可数名词，“许多”
He doesn't have much ( a great deal of ) money.
the number of “...的数目”The number of the students is 2000.
a number of = many 修饰可数名词，“许多”
We have many ( a number of ) friends here.