冠词分为不定冠词（a, an），定冠词（the），和零冠词。
1.指一类人或事，相当于a kind of
A plane is a machine that can fly.
2.第一次提及某人某物，非特指
A boy is waiting for you.有个男孩在等你。
3.表示“每一”相当于every，one
We study eight hours a day.
4.表示“相同”相当于the same
We are nearly of an age.
5.用于人名前，表示不认识此人或与某名人有类似性质的人或事
—Hello, could I speak to Mr. Smith?
—Sorry, wrong number. There isn't______ Mr. Smith here.
A. 不填 B. a C. the D. one
That boy is rather a Lei Feng.（活雷锋）
6.用于固定词组中
a couple of, a bit, once upon a time, in a hurry, have a walk, many a time
7.用于quite, rather, many, half, what, such之后
This room is rather a big one.
8.用于so(as, too, how)+形容词之后
She is as clever a girl as you can wish to meet.
