英语单词a 和 an怎样应用

1． 表示“一”这个数量概念,比one意思稍弱
e.g.:The plan will be ready in a week or two.
2． 表示某人或某物,但不具体说明哪个,相当于any
e.g.:This poem was written by a student.
注：在1,2两项中,如果名词变复数,把a换成数词或不定代词some,any等即可.
e.g.:The plan will be ready in three weeks.
3． 表示某一类人或事物
e.g.:Even a child can answer this question.
注：句中名词变复数时,去掉不定冠词a/an即可.
4． 和表示时间或度量衡的名词连用表示“每日”、“每斤”等
e.g.:I take a two-mile walk twice a day.
5． 用于固定词组
e.g.:have/take a shower have/take a bath
take a walk give a lecture
a lot of a couple of
as a rule have a headache
a few a little a bit
6.不定冠词用于有形容词修饰的季节,日期前面
The traffic accident happened on a Sunday towards the end of July.