（一）.不定冠词的用法
1.用在可数名词前表示
“一个”相当于“one”(类指)。There is a book on the desk.
I’ll return in a day or two.
2.用在专有名词前
,表示“某一个”相当于“a certain”.
A Mr. White is waiting for you downstairs.
3.表示“一类”
相当于“
any”(
泛指).A horse is a useful animal.
4.表示“每一”
相当于“
per”.
The doctor asked me to take the medicine three times a day.
The envelopes are one yuan and twenty fen a dozen
5.用在某些固定词组中
.a bit, a few, a little, a lot of, a piece of, a cup of, a glass of, a pile of, a pair of, have a good time, for a while, for a lo ...