a，是一个
不定冠词，也是字母表中第一个字母，通常后面加
名词。“a”意为“一个(可代替任意单
数量词，一般与one替换)”，如：一只老虎“a tiger”；一辆公共汽车“a bus”；一支铅笔“a pencil”。
涵义与造句
1.一个;任何一个
Would you like a drink?
你想喝点儿东西吗？
A dog has four legs.
狗有四条腿。
He's a teacher.
他是教师。
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2.每一个;对每一个来说
She phones her mother three times a week.
她每星期给母亲打三次电话。
This wine costs £4 a bottle.
这种葡萄酒4英镑一瓶。
a和an的区别
在读音以a、e、i、o或u开始的字之前，用 an ,不用 a 。
重要的是发音，不是拼写字母。
a box 一个盒子
a singer 一个歌唱者
a university 一所大学
an apple 一个苹果
an hour 一个小时
an MP 一位议员
应用
一辆汽车：a car
一辆公交车：a bus
一只猫：a cat
一个玩具：a toy
一支钢笔：a pen
一根香蕉：a banana
牛津词典
also an
indefinite article
【帮助说明】 The form a is used before consonant sounds and the form an before vowel sounds. When saying abbreviations like ‘FM’ or ‘UN’, use a or an according to how the first letter is said. For example, F is a consonant, but begins with the sound /e/ and so you say:
an FM radio.
U is a vowel but begins with /j/ and so you say:
a UN declaration.
a用于辅音前，an用于元音前。在FM、UN等缩略语前，用a还是an，需视首字母如何发音而定。如F是辅音字母，但其发音以 /e/ 开头，故应说：an FM radio。U是元音字母，但其发音以 /j/ 音开头，故应说：a UN declaration。
1.
（用于可数名词或单数名词前，表示未曾提到的）一（人、事、物）
used before countable or singular nouns referring to people or things that have not already been mentioned
a man/horse/unit
一个人；一匹马；一个单位
an aunt/egg/hour/x-ray
一个姑母；一个鸡蛋；一小时；一张X光片
I can only carry two at a time.
我一次只能带两个。
There's a visitor for you.
有位客人找你。
She's a friend of my father's (= one of my father's friends) .
她是我父亲的一位朋友。
2.
（用于前有形容词或后有短语的不可数名词前）
used before uncountable nouns when these have an adjective in front of them, or phrase following them
a good knowledge of French
精通法语
a sadness that won't go away
挥之不去的悲愁
3.
任何一；每一
any; every
A lion is a dangerous animal.
狮子是猛兽。
4.
（表示为某一群体或职业中的一员）
used to show that sb/sth is a member of a group or profession
Their new car's a BMW.
他们的新轿车是辆宝马。
She's a Buddhist.
她是个佛教徒。
He's a teacher.
他是教师。
Is that a Monet (= a painting by Monet) ?
那是莫奈的画吗？
5.
（用于视为一体的两个名词之前）
used in front of two nouns that are seen as a single unit
a knife and fork
一副刀叉
6.
（用于某些数字前，代替one）
used instead of one before some numbers
A thousand people were there.
那里有一千人。
7.
（用于价格、数量、比率等）一，每一
used when talking about prices, quantities and rates
同义词： per
They cost 50p a kilo.
其价钱是一公斤50便士。
I can type 50 words a minute.
我每分钟能打50个单词。
He was driving at 50 miles an hour.
当时他正以每小时50英里的速度驾车。
8.
像（某人）的人；…式的人物
a person like sb
She's a little Hitler.
她是个小希特勒。
9.
（用于某人姓名前，表示说话者不认识此人）有个
used before sb's name to show that the speaker does not know the person
There's a Mrs Green to see you.
有位格林太太要见你。
10.
（用于一星期中某天的名称前，表示具体某一天）
used before the names of days of the week to talk about one particular day
She died on a Tuesday.
她是在一个星期二去世的。
习语
n.
from A to B
从一地到另一地
from one place to another
For me a car is just a means of getting from A to B.
在我看来，汽车只不过是从一地到另一地的代步工具。
from A to Z
从头到尾；彻底地；完全
including everything there is to know about sth
He knew his subject from A to Z.
他通晓自己的学科。
衍生
a few 少数；几个
a good few 相当多，不少，颇有
a good many 相当多，很多
a great many 许许多多，极多，为数极大
quite a few 很多；许多；相当多