a和an用法顺口溜：不定冠词a和an,单数可数名词前;辅音若在词首发,词前只把a来加;元音若在词首放,词前an词不敢忘;不定冠词相当one,但不强调数观念;不定冠词很关键,四个所指记心间.(每指、泛指、类指和某指)
不定冠词a和an的用法顺口溜
不定冠词a和 an, a后辅音an后元，
泛指一类或一个，表数语气比one弱,
序数词前表又再，most前意非凡，
抽象物质动变名，化为具体用法灵，
用错a/an被人笑，单名泛指被丢掉，
指代物代所有连，位置放错更无颜。
不定冠词a/an的用法
不定冠词有两个，a 和 an。a用在辅音开头的单词前面;an用于以元音开头的单词前。如：a book, an apple。具体用法如下：
1)表示“一个”、“某一个”、“ 每一”、“再一，又一”、或“同一，相同”等
Eg：
Rome is not built in a day.
A Mr. Smith is waiting for you at the school gate.
He usually works eight hours a day.
You can try it a second time if you fail.
They are of an age./ Birds of a feather flocks together.
2)泛指某一类人或物，意为“任何一个，任一”
Eg:
A square has four sides.
3)当物质名词具体化表示“一(类、阵、份)”等;抽象名词具体化为“……的人或者事”时
Eg:
Green tea is a wonderful tea.
We don’t have much rain here, but last night we had a heavy rain.
Reading is a pleasure for me.
The meeting is a great success.
4)表示季节、月份、日期、三餐的名词，或表示世上独一无二的物体名词前有形容词修饰时
Eg:
We have a every cold winter last year.
This happened on a rain Sunday towards the end of May.
We hope we can see a full moon tonight.
5)源于动词的名词与take/have 连用时
Take a look; take a walk; have a break; have a visit to…
6)其他不定冠词a/an的用法(固定搭配)
All of a sudden; as a matter of fact; as a result; as a rule; as a whole; ata distance; in a way; in a hurry; in a sense; in a word; do sb. a favour; have agood time; have a word with ; go for a walk; make a difference; make a fool ofoneself; make a living; pay a visit to ; take an interest in; tell a lie; agood/wise knowledge of; a danger/threat to sb.; come as a surprise/shock; wishsb. a Merry Christmas…
