表示数目多少或顺序多少的词叫数词,数词分为基数词和序数词。表示数目多少的数词叫基数词;表示顺序的数词叫序数词。
一、基数词
1)基数词写法和读法: 345 three hundred and forty-five;
2)基数词一般是单数形式,但下列情况,常用复数:
a. 与of 短语连用,表示概数,不能与具体数目连 用,如scores of people 指许多人;
b. 在一些表示一排或一组的词组里;
如:They arrived in twos and threes. 他们三三两两的到达了。
c. 表示几十岁
d. 表示年代,用 in +the +数词复数;
e. 在乘法运算的一种表示法里,如:3 x 5 = 15 Three fives is fifteen.
二、序数词
序数词的缩写形式: first---1st second---2nd thirty-first---31st
三、 数词的用法
1)倍数表示法
a. 主语+谓语+倍数(或分数)+ as + adj. + as
I have three times as many as you. 我有你三倍那么多。
b. 主语+谓语+倍数(分数)+ the size of
The earth is 49 times the size of the moon. 地球是月球的49倍。
c. 主语+谓语+倍数(分数)+ 形容词(副词)比较级+ than
The grain output is 8 percent higher this year than that of last year.
今年比去年粮食产量增加8%。
d. 还可以用by+倍数,表示增加多少倍
The production of grain has been increased by four times this year.
今年粮食产量增加了4倍。
2)分数表示法
构成:基数词代表分子,序数词代表分母。分子大于1时,分子的序数词用单数,分母序数词用复数:
1/3 one-third ; 3/37 three and three-sevenths.
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