the number of sth 做主语谓语动词用单数还是复数

the number of+名词作主语，谓语动词用单数。
而A number of + 名词作主语，谓语动词用复数。

主语是“ a number of+ 复数名词”时，谓语动词要用复数形式；若主语是“ the number of+ 名词”时，谓语动词则要用单数形式。例如：

The number of the people invited was fifty, but a number of them were absent for different reasons.

the number of 是......的数量的意思，谓语动词必须接单数。
如：The number of the students in our school is 235.
a number of 是许多的意思，相当于a lot of.谓语动词用复数。
如：A number of people were injured in the terrible earthquake.

the number of+复数名词作主语，意思是“。。。。。的数量，数目”， 谓语动词用单数。
而A number of +复数 名词作主语，意思是“许多。。。。。。”， 谓语动词用复数。

the number of+名词作主语，谓语动词用单数
A number of + 名词作主语，谓语动词用复数