a

indefinite article

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
   1. a man/horse/unit
      一个人；一匹马；一个单位
   2. an aunt/egg/hour/x-ray
      一个姑母；一个鸡蛋；一小时；一张X光片
   3. I can only carry two at a time.
      我一次只能带两个。
   4. There's a visitor for you.
      有位客人找你。
   5. 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
   1. a good knowledge of French
      精通法语
   2. a sadness that won't go away
      挥之不去的悲愁
3. 任何一；每一
   any; every
   1. 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
   1. Their new car's a BMW.
      他们的新轿车是辆宝马。
   2. She's a Buddhist.
      她是个佛教徒。
   3. He's a teacher.
      他是教师。
   4. 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
   1. 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
   1. 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
   1. They cost 50p a kilo.
      其价钱是一公斤50便士。
   2. I can type 50 words a minute.
      我每分钟能打50个单词。
   3. 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
   1. 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
   1. 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
    1. She died on a Tuesday.
       她是在一个星期二去世的。

A or an is the indefinite article. It is used at the beginning of noun groups which refer to only one person or thing. The form an is used in front of words that begin with vowel sounds.
a 或 an 为不定冠词，用于表示单个事物或人的名词词组之前。an 用于以元音开始的单词之前。

1. DET （指初次提及或非特指的人或物）一（个）
   You use a or an when you are referring to someone or something for the first time or when people may not know which particular person or thing you are talking about.
   1. A waiter entered with a tray...
      侍者端着托盘进来了。
   2. He started eating an apple...
      他开始吃苹果。
   3. Today you've got a new teacher taking you...
      今天有位新老师来教你们。
   4. I manage a hotel.
      我经营一家旅馆。
2. DET （一类人或事物中非特指的）任何一（个）
   You use a or an when you are referring to any person or thing of a particular type and do not want to be specific.
   1. ...expensive make-up that we saw being advertised by a beautiful model...
      我们所见的由一位漂亮模特代言的昂贵化妆品
   2. I suggest you leave it to an expert...
      我建议你把它留给专家来解决。
   3. Bring a sleeping bag...
      带只睡袋。
   4. I was waiting for a bus.
      我在等公共汽车。
3. DET （用于前加形容词或后加修饰语的不可数名词之前）一（种）
   You use a or an in front of an uncount noun when that noun follows an adjective, or when the noun is followed by words that describe it more fully.
   1. There was a terrible sadness in her eyes...
      她眼神中流露出深深的悲伤。
   2. He did have a real knowledge of the country...
      他对该国的确知之甚多。
   3. Baseball movies have gained an appreciation that far outstrips those dealing with any other sport.
      以棒球为主题的电影获得的青睐远远超过了其他体育类电影。
4. DET （用于物质名词前）一（类），一（种）
   You use a or an in front of a mass noun when you want to refer to a single type or make of something.
   1. Bollinger 'RD' is a rare, highly prized wine.
      博林格RD香槟是一种名贵的备受推崇的葡萄酒。
5. DET （用于表示数量的词组中）许多/少许/一点
   You use a in quantifiers such as a lot ,a little, and a bit.
   1. I spend a lot on expensive jewelry and clothing...
      我花很多钱购买昂贵的首饰和衣服。
   2. I've come looking for a bit of advice.
      我特来讨教。
6. DET （一类人或事物中典型的）一（个）
   You use a or an to refer to someone or something as a typical member of a group, class, or type.
   1. Some parents believe a boy must learn to stand up and fight like a man.
      有些父母认为男孩子必须学会像男子汉一样顶天立地，勇于抗争。
   2. ...the operation a patient has had.
      病人做过的手术
7. DET （用于日子、月份或节日的名称之前以表示特例）一个
   You use a or an in front of the names of days, months, or festivals when you are referring to one particular instance of that day, month, or festival.
   1. The interview took place on a Friday afternoon...
      采访是在一个星期五的下午进行的。
   2. It was a Christmas when shoppers passed by expensive silks in favor of more practical gifts.
      这是一个购物者不理会昂贵的丝绸衣服而热衷于更实用礼物的圣诞节。
8. DET （从事某一职业的）一（位），一（名）
   You use a or an when you are saying what someone is or what job they have.
   1. I explained that I was an artist...
      我解释说自己是个艺术家。
   2. He was now a teacher and a respectable member of the community.
      他现在是一位教师，并且是社区内受人尊敬的一员。
9. DET （用于不为说话人所知的首次提到的人名前）某一（个）
   You use a or an in front of the names of people as a way of indicating that you do not know them or anything about them and you are saying their name for the first time.
   1. The full address on a stick-on label was that of a Mrs P. R. Slater of Peterborough...
      不干胶标签上的完整地址写的是彼得伯勒的一位P. R. 斯莱特太太。
   2. A Dr Matthew Owens was reported missing while on an expedition to north-eastern Turkey.
      据报道，一位叫马修·欧文斯的博士在前往土耳其东北部考察的途中失踪了。
10. DET （用于人名前，表示与该人有相同特性或品质）类似…的一个（或一位）
    You use a or an in front of the names of people when you want to refer to someone else who has the same qualities or character as the person named.
    1. When I listen to her play I can hear a new Nigel Kennedy.
       从她的演奏中我听出了新一代的奈杰尔·肯尼迪。
11. DET （用于姓氏前，表示某人属于某姓氏家族）一位姓…的人
    You use a or an in front of a surname when you want to refer to someone who belongs to the family with that surname.
    1. As far as I can recall, Patti was a Smith.
       我记得帕蒂是姓史密斯的。
12. DET （用于艺术家名字前）一幅…的画，一件…的雕塑作品
    You use a or an in front of the names of artists to refer to one individual painting or sculpture created by them.
    1. Most people have very little difficulty in seeing why a Van Gogh is a work of genius.
       多数人不难理解为什么凡·高的作品是天才之作。
13. DET （代替数字one使用，尤用于hundred，hour和metre等表示度量的单词之前以及half, quarter和third等分数之前）
    You use a or an instead of the number 'one', especially with words of measurement such as 'hundred', 'hour', and 'metre', and with fractions such as 'half', 'quarter', and 'third'.
    1. ...more than a thousand acres of land.
       1,000多英亩地
    2. ...a quarter of an hour...
       一刻钟
    3. The skirts were shortened an inch or two.
       这些裙子被改短了一两英寸。
14. DET （用于表示比率的短语中）每一
    You use a or an in expressions such as eight hours a day to express a rate or ratio.
    1. Prices start at £13.95 a metre for printed cotton...
       印花棉布以每米13.95英镑的价格起售。
    2. The helicopter can zip along at about 150 kilometres an hour.
       该直升机能以每小时150公里左右的速度疾进。

1. A waiter entered with a tray
   侍者端着托盘进来了。
2. Today you've got a new teacher taking you
   今天有位新老师来教你们。
3. I manage a hotel.
   我经营一家旅馆。
4. Bring a sleeping bag
   带只睡袋。
5. I was waiting for a bus.
   我在等公共汽车。
6. There was a terrible sadness in her eyes
   她眼神中流露出深深的悲伤。
7. He did have a real knowledge of the country
   他对该国的确知之甚多。
8. Bollinger 'RD' is a rare, highly prized wine.
   博林格RD香槟是一种名贵的备受推崇的葡萄酒。
9. I spend a lot on expensive jewelry and clothing
   我花很多钱购买昂贵的首饰和衣服。
10. I've come looking for a bit of advice.
    我特来讨教。
11. Some parents believe a boy must learn to stand up and fight like a man.
    有些父母认为男孩子必须学会像男子汉一样顶天立地，勇于抗争。
12. The interview took place on a Friday afternoon
    采访是在一个星期五的下午进行的。
13. It was a Christmas when shoppers passed by expensive silks in favor of more practical gifts.
    这是一个购物者不理会昂贵的丝绸衣服而热衷于更实用礼物的圣诞节。
14. He was now a teacher and a respectable member of the community.
    他现在是一位教师，并且是社区内受人尊敬的一员。
15. The full address on a stick-on label was that of a Mrs P. R. Slater of Peterborough
    不干胶标签上的完整地址写的是彼得伯勒的一位P.R.斯莱特太太。
16. A Dr Matthew Owens was reported missing while on an expedition to north-eastern Turkey.
    据报道，一位叫马修·欧文斯的博士在前往土耳其东北部考察的途中失踪了。
17. When I listen to her play I can hear a new Nigel Kennedy.
    从她的演奏中我听出了新一代的奈杰尔·肯尼迪。
18. As far as I can recall, Patti was a Smith.
    我记得帕蒂是姓史密斯的。
19. Most people have very little difficulty in seeing why a Van Gogh is a work of genius.
    多数人不难理解为什么凡·高的作品是天才之作。
20. It's not a question of some abstract concept.
    这不是某个抽象概念的问题。
21. A man had accosted me in the street.
    一个男的在街上和我搭讪。
22. I set off for a new adventure in the United States on the first day of the new year.
    新年第一天，我在美国开始了一次新的冒险。
23. This man is an animal, a beast
    这人是个畜生，是个野兽。
24. This is the end of a tour so I'm a little antsy, I guess.
    旅途就此结束了，这让我有点坐立不安，我想是吧。
25. I autographed a copy of one of my books.
    我在自己的一本书上签了名。
26. The research begs a number of questions.
    研究绕过了一些问题。
27. I had the beginnings of a headache
    我有了头痛的先兆。
28. I was in a market in Tangier and bingo! I found this.
    当时我正在丹吉尔的一个市场里。瞧！我发现了这个。
29. She's just given birth to a baby girl
    她刚生了一个女孩。

  a (an) one【导航词义：一个】

  a (an) indef. art. 一个

〔辨析〕通常用于单数可数名词之前，泛指某类人或事物中的一个。

  one num. 一，一个

〔辨析〕强调数量的概念，说明是一个而不是两个或三个。

n.

from A to B

• 从一地到另一地
  from one place to another
  1. 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
  1. He knew his subject from A to Z.
     他通晓自己的学科。

noun

1. the 1st letter of the Roman alphabet

   Synonym:    A