【问】 the number of与a number of有什么区别?
 【答】 the number of与a number of在语义上是完全不同的。前者意为：“……的数目”，后者意为“许多”(=many)、“若干”：
 1. I want to know the number of the motor-vehicles.
 我想了解机动车的数目。
 2. The number of books missing from the library is large.
 图书馆丢失的图书数量是很大的。
 3. I have a number of reasons.
 我有许多理由。
 4. A number of students were absent yesterday.
 昨天有一些学生缺席。
 其次，由于the number of是指事物的数目这一概念，所以，它的谓语动词要用单数：
 1. The number of competitors is limited.
 参赛者的数目是有限的。
 2. The number of jobless people grows.
 失业人数在增加。
 而a number of是指“许多……”、“一些”，所以它的谓语动词要用复数：
 1. There were a number of people out this afternoon.
 今天下午有许多人外出。
 2. A number of accidents have accurred.
 发生了一些事故。
 请做下面的英语试题：
 1. “Why is the university doing so much building?”“ The number of students ____. ”
 A. have increased so rapidly B. has increased so rapid
 C. have increased so rapid D. has increased so rapidly (TOEFL，70. 6)
 2. The number of people invited_______fifty，but a number of them_______absent for different reasons.
 a. were; was B. was; was C. was; were D. were; were(全国高考英语试题，1996)
 [参见a(a number of... is/are)]