知识点总结
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.
c. 表示"几十岁",如 in his thirties
d. 表示"年代",用 in +the +数词复数;如in the 1980s
e. 在乘法运算的一种表示法里,如:3 x 5 = 15 Three fives is (are) 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.
b. 主语+谓语+倍数(分数)+ the size (amount,length…) of…
The earth is 49 times the size of the moon.
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.
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.
2)分数表示法
构成口诀:分子基数词,分母序数词。分子大于1,分母加-s:
1/3 one-third ; 3/37 three and three-sevenths
误区提醒
1. 对基数词的形式掌握不清;2.对概数的表达词组掌握不清;3.倍数的表达行形式混淆不清。
【典型例题】
1.The tsunami killed ____ people in south and southeast Asia.
A.ten thousands B. ten thousands of
C. tens of thousand D. tens of thousands of
解析:错选B。当hundred, thousand, million, billon 等数量单位前有具体数字时不要用复数,表概数时其后加s且后加of。因此“几十万”的表达应为“tens of thousands of”,正确答案C。
2.At a rough estimate,Nigeriais ___Great Britain.
A. three times the size as B. the size three times of
C. three times as the size of D. three times the size of
解析:错选A。倍数的表达方法不再赘述,见上面讲解。正确答案D。