不定冠词“a”用来表示可数名词的单数形式，用于辅音音素前，an用于元音音素前。

如：a person, a day; an hour, anold man...

I.定冠词用法如下：

(英语刚启蒙时你就知道冠词了，可你真正掌握了吗?再背一遍又何妨?!)

1.用于双方都知道的名词前：Please cleanthe classroom.

2.用于单数名词前，表示一类人或物：

The horseis a useful animal.(马是有用的动物)

This is a very hardjob for theteacher.(对于老师这是一项很难的工作。)

3.用于世界上独一无二的东西前：the sun, the spring.

4.用于方位名词前：People in the west like coffee very much.

5.用于乐器名词前：play the violin.

6.用于计量单位前：Gasoline is soldby the gallon.

7.形容词级和序数词前：This is the easiest way to work out the problem.

He came to see me for first time.

8.用于江河湖海山脉名称前：the Pacific，the Thames，the Rocky Mountains

9.杂志、报刊名称前：the Times，the Overseas Digest

10.用于建筑物、和组织前：the White House, theMinistry of Education

11.用于姓氏复数前，表“某某夫妇，某某一家人”the Smiths，the Greens

12.用于形容词前，表一类人 / 物：the rich, theblind

13.用于 English，Chinese，French等名词前，表“全体国民”the English，the Chinese