number

1.Room Number 123, bus number 73等表达方式里在Room, bus等词前面没有the。

2.a number of （许多）后面必须接复数形式的名词或代词，动词有时用复数，有时用单数，如A number of boys（或them）are（或is）in the next room和A large number of books are（或is）lent at the library every day。有人以为用单数形式的动词不算正当。

比较下面两句：

• An increasing number of pupils have made use of the library.
• An increasing number of pupils has made it necessary to keep more copies of the same books.

第一句着重在“更多的学生”，第二句着重在学生数的增加。

3.在公文里往往把in a number of cases用作often解。