1.a / an 表示数量 “一”,但不强调数量 “一”.如果强调数量“一”,应该用one.请比较:
I have a brother.
(想告诉别人:“我”有兄弟,虽然提到了 “一个”,但想强调的是 “我”不是独生子女,或想强调的是 “我”不是有姐妹.)
I have only one brother.
(想告诉别人:“我”并没有两个、三个兄弟.)
2.不表示数量 “一”,而是表示类别,可以在单数可数名词前加a /an.
A horse runs faster than an elephant.
注意:也可以在单数可数名词前加the或在复数可数名词前不加 任何冠词表示类别.不可数名词表示类别时不加任何冠词.例如:
The horse runs faster than the elephant.
Horses run faster than elephants.
One can not live without air or water.
3.对于说话者特指但听话者还不知的单数可数名词(人或物),第一 次提到时,前面经常加a / an;再次提到才加the,这时,说话者和听话者都知道是特指哪一个人或物.
At a science museum in Canada,you can feel your hair stand on end as harmless electricity passes through your body.Last year I was lucky enough to have a chance to visit the museum.
I bought a computer 3 years ago,but I have sold the computer (=it) already.
4.在形容词、现在分词或过去分词前加the可以表示一类人或物,且表示复数.
the poor,the sick,the following,the wounded,the English,the French
5.在最高级副词前可以加the,也可以不加the;在最高级形容词前 一般要加the; 但是,如果不表示 “最”,而是表示“非常”,则应 在最高级形容词前加 a / an,
She sings (the) most beautifully in our school.
Xiamen is the most beautiful city in Fujian Province.
Xiamen is a most (=very) beautiful city.
6.在序数词前一般要加the表示顺序;但如果表示数量的增加,表示“又一…”,相当于 “another”的意思,则要在序数词前加 a / an.
This is the second time that I have seen the film.
I’ve had two cakes,but I’d like a third (=another) one.
7.提到了“演奏”的乐器前和提到了“发明”的物名前要加 the.
She often practises playing the piano after supper.
(比较:There is a piano near the window of the living room.)
---What do you think was the most useful invention in the 20th century?
---The cell phone,I think.
Who invented the cell phone?
(比较:Do you own a telephone?)
8.在世界上独一无二的名词和含有普通名词的专有名词前要加the.
the world,the moon
(比较:Sitting down in front of their computers,they leave a familiar world and enter a place where things act instrange ways.)
the United States of America,the Great Wall
建议你买一本语法书,好好看看,钻研,一定要理解透,相信你完全可以掌握的!