不要用中文去理解英文的语法，这里的“a”是不定冠词！是指一类，不是单独一个！

不定冠词a(an) 的使用

1. what 后的感叹句中,若感叹的名词是可数名词单数,不定冠词a/an不能省略.如:

What a horrible day!

2. a/an 用于指非独一无二的工作或职业.如

She is a teacher.

He's a bank manager.

但如果一个名词用作表语、同位语,表示某人当时或现在独一无二的职位或头衔时,通常其前不用冠词(间或用the).如:

He is Secretary of State, but he will be President of this small country.

As Chairman of the committee, he will declare the opening of the meeting.

3. 疾病名称通常被认为是不可数的,因此,其前通常不加冠词.如:

The three Brontè sisters died of tuberculosis. 简氏三姐妹均死于肺结核.

She's had appendicitis. 她得了阑尾炎.

In the first half of last century, many children died of measles. 上世纪前半叶,许多孩子死于麻疹.

但谈到cold, 我们通常说a cold, 如 catch a cold, have (get) a cold.

同样我们说a stomachache, a headache.如:

I've got a headache today. 但其他的ache(backache, toothache, earache, etc)在英国英语中均不可数,无须任何冠词

以上所列举的均是一些与冠词有关、有规律可寻的用法,但英语中也有为数不少的固定短语,它们或用冠词,或不用冠词(可称为零冠词),或用定冠词,或用不定冠词,其中没有任何规律可寻.我们将这些称为习惯搭配.下面就是大学英语四级考试中常遇到的一些固定搭配、或与冠词有关的表达,希望同学们在平时的英语学习中能多加注意.

1. 习惯用定冠词的表达

by the way, on the whole, in the end, on the way to, tell the truth, on the right / left, in the possession of, be in the habit of doing sth., on the spot, the day before yesterday, in the distance, in the case of, for the time being, at the hands of, in the front of, be in the dark, at the back of, to the extent of等.

2. 习惯用不定冠词的表达

as a matter of fact, as a rule, be in a position to, a matter of course, all of a sudden, be at a loss, have a chance, have a good time, have a hand in, have a say, have a try, keep an eye on, on a large scale, with a firm hand, take a fancy to, be in a hurry, take a walk, take an interest in等.

3. 习惯用零冠词的表达

at noon/night/dawn/midnight, in town, in front of, at bottom, in order, in peace, at hand, at home, at last, at present, at stake, at war, by way of, day and night, without result, on top of, in trouble, in sight, from beginning to end, in advance, in haste, in danger, in case(of), in possession of, in fashion, in fact, take part in, take place等.

以上所列固定词组有时无法解释为什么用或不用冠词,因此在日常的学习中我们不妨将它们当作成语来记忆和使用.若能将这些有关的知识掌握并加以运用,相信会为我们的英语学习带来许多方便.