1． 表示“一”這個(gè)數(shù)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,但不具體說(shuō)明哪個(gè),相當(dāng)于any
e.g.:This poem was written by a student.
注：在1,2兩項(xiàng)中,如果名詞變復(fù)數(shù),把a(bǔ)換成數(shù)詞或不定代詞some,any等即可.
e.g.:The plan will be ready in three weeks.
3． 表示某一類(lèi)人或事物
e.g.:Even a child can answer this question.
注：句中名詞變復(fù)數(shù)時(shí),去掉不定冠詞a/an即可.
4． 和表示時(shí)間或度量衡的名詞連用表示“每日”、“每斤”等
e.g.:I take a two-mile walk twice a day.
5． 用于固定詞組
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.不定冠詞用于有形容詞修飾的季節(jié),日期前面
The traffic accident happened on a Sunday towards the end of July.