有些名词在一种场合下属于这一类，在另一种场合下又属于那一类。例如有些物质名词也可用作个体名词，意思上有一定变化：
glass玻璃－a glass玻璃杯       iron铁－an iron熨斗
copper铜－a copper铜币        tin锡－a tin洋铁罐
paper纸－a paper报纸，证件    wood木头－a wood树林
又如一些抽象名词，当意思转变而表示某类个体时，就成了个体名词：
youth青春－a youth青年人      relation关系－a relation亲属
democracy民主－a democracy民主国家   authority权威－an authority权威人士
power威力，电力－a power大国      necessity必要性－a necessity必需品
beauty美－a beauty每人，美的东西

练习题：
1、---What would you like to drink, ________ or orange?
   ---Orange, please. (2004年佛山市中考试题)
   A. hamburger      B. chip       C. tea     (C)
2、When we saw his face, we knew___ was bad.
A. some news B. a news C. the news P. news   (C)
3、In England, if ____ is in the middle of the day, the evening meal is called supper.
　 A. food   B. lunch   C. breakfast   D. dinner   （B）
4、What’s your _______ for being late again?
　 A. idea   B. key   C. excuse   D. news    (C)
5、Where are the students? Are they in _______ ?  
　 A. the Room 406   B. Room 406   C. the 406 Room   D. 406 Room     (B)

6、The teacher said we needed to choose three        for the school concert.  （2006 重庆）
   A. farmers       B. doctors       C. drivers       D. singers    (D)
7、－What class are you in, Mike?
   －I’m in       .
A. Grade Three, Class Two      B. Class Two, Grade Three

C. class two, grade three        D. grade three, class two         (B)