a number of the number of 区别

1、意思不同
a number of 相当于 a lot of, many，意思是：许多，一些。 the number of意思是......的数。
The number of sick students is decreasing.生病学生的数量在减少。
A number of students are sick today. 今天一些学生病了。
2、用法不同
a number of 后面动词用复数，the number of 后面动词用单数。
A number of houses were burnt down in the fire. 在火灾中，许多房子给烧毁了。
The number of business failures has risen.企业倒闭的数量增加了。
3、名词用法不同
the number of 表示“……的数目（号码）”，of 后跟复数名词。a number of 相当于many ,意为“许多”，后跟复数名词或代词。number前可用large,small等修饰,以表示程度。
The number of students in this class is 40.（正）这个班的学生数是40。
A number of students are planting trees on the hill．许多学生在小山上植树