什么时候不用冠词？

- 泛指某一类人、事、物时，复数的可数名词以及不可数名词前面不需要冠词：
Cats are beautiful animals. 
猫是很漂亮的动物。[泛指所有猫]
British people are often polite. 
英国人通常很有礼貌。[泛指英国人]
Tea is good for you.
茶对你（身体）有益。[泛指茶]

相应地，特指具体某人、事、物时，要用冠词the：
Cats are beautiful animals. The cats who live next door are Siamese.

Siamese 暹罗的

猫是很漂亮的动物。住在隔壁的猫是暹罗猫。[The cats特指的是住在隔壁的猫，而不是所有的猫]

British people are often polite. The British people I know are very reserved. 
reserved 内敛的，矜持的，含蓄的
英国人通常很有礼貌。我认识的英国人很矜持内敛。[The British people特指我认识的英国人，而不是所有英国人]

Books are so important in my life.
书在我的生活中是如此重要。[books泛指所有书]
The books were all over the floor.
地板上到处都是书。[the books特指我和对方都知道的那些书]

- 限定词（my/your/his/her, this/that, any, some）前面不用冠词：
I love my job. 我爱我的工作。
X I love the my job.
Does she want this book? 她想要这本书吗？
X Does she want the this book?

- 习惯搭配
go to bed
I always go to bed at eleven o'clock.
我总是在十一点睡觉。

X I always go to the bed …

go to work
They go to work at 8 am every morning.
他们每天早上8点去上班。
X They go to the work …

(be) at school
(be) at the school
When I was at school, we didn't have computers.
我上学的时候，我们没有电脑。[at school指的是作为学生，在学校……]
When I was at the school … 
当我在学校的时候……[at the school指的是在学校的建筑里……]

(be) in hospital
(be) in the hospital
She didn't want to be in hospital but she was too ill to go home.
too...to... 太……而不能……
ill 生病的，有病的
她不想住院，但她病得太重，不能回家。[in hospital指的是作为患者，住在医院里……]
She didn't want to be in the hospital … (in the hospital means being in the building)
她不想待在医院……[in the hospital指的是在医院楼里……]