①辅音音素开头的单数名词前用a;元音音素开头的单数名词前用an。 a giraffe a ladder an apple an eggplant Notice:这里所指的是元音音素前用an,并非是元音字母前。 an hour an honest student a one-yuan note a European country a UFO ②字母a, e, f, h, i, l ,m, n, o, r, s, x视为独立单词使用时,这些字母前要用an. There’s an “s” and a “u” in the word “sun”. ③以元音字母u开头的单词前选用a/an,要视以下两种情形而定: A.发[Q]时,前用an an uncle an umbrella an unusual day B.发[ ju: ]时,前用a a uniform a useful book a university ⑵不定冠词a/an的用法 ①表示第一次提到的人或事物。 There’s a suitcase under the bed. The suitcase is very heavy. ②表示泛指。 I want a new pencil-box. ③表示数量“一”,相当于one。 A plane can cover 800 kilometres in an hour. ④序数词前加a/an,不表示“第…”而是“又一个”、“又一次”等。 I am going to learn a second language. ⑤用于不可数名词转化的可数名词前。 a coffee a beer ⑥用于姓氏名词前,表示“一位…”。 A Mr smith is waiting for you in the office. ⑦表示某一种类。 A horse is a useful animal. ⑧用在一些表示数量的词组中。 a little a few a set of a large number of a lot of a piece of a group of a huge amount of ⑨用在其它一些固定搭配中。 have a good time have a look in a hurry have a talk/word with have a try do sb a f