英汉词典

a 基本解释

• n. 字母A；第一流的；学业成绩达最高标准的评价符号
• abbr. [物]安（ampere）

a 中文词源

不定冠词an在发展过程中出现的缩略形式，应用于首字母为辅音的单词及h发音单词。

a 英文词源

a

a: [OE] The indefinite article in English is ultimately identical with the word one (as is the case, even more obviously, in other European languages – French un, German ein, and so on). The ancestor of both a(n) and one was ān, with a long vowel, but in the Old English period it was chiefly used for the numeral; where we would use a(n), the Anglo-Saxons tended not to use an article at all. Ān begins to emerge as the indefinite article in the middle of the 12th century, and it was not long before, in that relatively unemphatic linguistic environment, its vowel became weakened and shortened, giving an.

And at about the same time the distinction between an and a began to develop, although this was a slow process; until 1300 an was still often used before consonants, and right up to 1600 and beyond it was common before all words beginning with h, such as house.
=> one

a (1)

indefinite article, mid-12c., a variation of Old English an (see an) in which the -n- began to disappear before consonants, a process mostly complete by mid-14c. The -n- also was retained before words beginning with a sounded -h- until c. 1600; it still is retained by many writers before unaccented syllables in h- or (e)u-, but is now no longer normally spoken as such. The -n- also lingered (especially in southern England dialect) before -w- and -y- through 15c.

a (2)

as in twice a day, etc., from Old English an "on," in this case "on each." The sense was extended from time to measure, price, place, etc. The habit of tacking a onto a gerund (as in a-hunting we will go) died out 18c.

a 英文释义

1. the blood group whose red cells carry the A antigen

2. a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation

3. any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes

4. one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)

5. (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA

6. the basic unit of electric current adopted under the Systeme International d'Unites;

"a typical household circuit carries 15 to 50 amps"

7. the 1st letter of the Roman alphabet

a 双语例句

1. Liver and kidney are particularly rich in vitamin A.

肝脏和肾脏富含维生素A。

来自柯林斯例句

2. Details are available from the Hon. Sec. A.R. Bushby.

详情可咨询名誉秘书A.R.布什比。

来自柯林斯例句

3. I was assigned to Troop A of the 10th Cavalry.

我被派往第10骑兵队的A连。

来自柯林斯例句

4. Passes are graded from "A" down to "E".

及格分为A到E几等。

来自柯林斯例句

5. Use only clean, Grade A, perfect eggs.

只用表面干净、无磕碰的A级鸡蛋。

来自柯林斯例句

a 实用场景例句

a good knowledge of French

精通法语

牛津词典

I can only carry two at a time.

我一次只能带两个。

牛津词典

There's a visitor for you.

有位客人找你。

牛津词典

She's a friend of my father's (= one of my father's friends) .

她是我父亲的一位朋友。

牛津词典

a man/horse/unit

一个人；一匹马；一个单位

牛津词典

an aunt/egg/hour/x-ray

一个姑母；一个鸡蛋；一小时；一张X光片

牛津词典

...a quarter of an hour...

一刻钟

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

...more than a thousand acres of land.

1,000多英亩地

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

As far as I can recall, Patti was a Smith.

我记得帕蒂是姓史密斯的。

柯林斯高阶英语词典

I explained that I was an artist...

我解释说自己是个艺术家。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

There was a terrible sadness in her eyes...

她眼神中流露出深深的悲伤。

柯林斯高阶英语词典

He did have a real knowledge of the country...

他对该国的确知之甚多。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

I spend a lot on expensive jewelry and clothing...

我花很多钱购买昂贵的首饰和衣服。

柯林斯高阶英语词典

I've come looking for a bit of advice.

我特来讨教。

柯林斯高阶英语词典

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。

柯林斯高阶英语词典

...the operation a patient has had.

病人做过的手术

柯林斯高阶英语词典

The interview took place on a Friday afternoon...

采访是在一个星期五的下午进行的。

柯林斯高阶英语词典

...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

柯林斯高阶英语词典

I suggest you leave it to an expert...

我建议你把它留给专家来解决。

柯林斯高阶英语词典

A waiter entered with a tray...

侍者端着托盘进来了。

柯林斯高阶英语词典

He started eating an apple...

他开始吃苹果。

柯林斯高阶英语词典