时间:2018-12-01 作者:英语课 分类:高中语法汇总


英语课

数词


.概念:


   数词分两类:基数词和序数词.表示数目的词叫基数词,表示须序的词叫序数词.


.相关知识点精讲


 1.基数词


  1)基数词一般可写成如345three hundred and forty-five


  2)基数词一般是单数形式,但遇下列情况,常用复数:


   a. 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""一组"的词组里。例如:


They arrived in twos and threes. 他们三三两两的到了。


   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Three fives isarefifteen


2.序数词


   序数词的缩写形式如first---1st second---2nd thirty-first---31st等。 


3.数词的用法


  1)倍数表示法


   a. 主语+谓语+倍数(或分数)+ as + adj. + as。例如


    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 amountlength…) of…。例如:


    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…。例如:


     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。例如:


   The production of grain has been increased by four times this year. 今年粮食产量增加了4倍。


  2)分数表示法的构成: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。例如:


     1/3   one-third 3/37    three and three-sevenths.


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