二、序数词

序数词的缩写形式： first——1stsecond——2ndthirty-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 (amount，length…) 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.