表示數(shù)目多少或順序多少的詞叫數(shù)詞,數(shù)詞分為基數(shù)詞和序數(shù)詞。表示數(shù)目多少的數(shù)詞叫基數(shù)詞;表示順序的數(shù)詞叫序數(shù)詞。

    一、基數(shù)詞

    1)基數(shù)詞寫法和讀法: 345 three hundred and forty-five;

    2)基數(shù)詞一般是單數(shù)形式,但下列情況,常用復(fù)數(shù):

     a. 與of 短語連用,表示概數(shù),不能與具體數(shù)目連 用,如scores of people 指許多人;

     b. 在一些表示"一排"或"一組"的詞組里;

    如:They arrived in twos and threes. 他們?nèi)齼蓛傻牡竭_(dá)了。

     c. 表示"幾十歲";

     d. 表示"年代",用 in +the +數(shù)詞復(fù)數(shù);

     e. 在乘法運(yùn)算的一種表示法里,如:3 x 5 = 15 Three fives is (are) fifteen.

   二、序數(shù)詞

    序數(shù)詞的縮寫形式: first---1st second---2nd thirty-first---31st 

   三、 數(shù)詞的用法

    1)倍數(shù)表示法

     a. 主語+謂語+倍數(shù)(或分?jǐn)?shù))+ as + adj. + as

      I have three times as many as you. 我有你三倍那么多。

     b. 主語+謂語+倍數(shù)(分?jǐn)?shù))+ the size (amount,length…) of…

      The earth is 49 times the size of the moon. 地球是月球的49倍。

     c. 主語+謂語+倍數(shù)(分?jǐn)?shù))+ 形容詞(副詞)比較級(jí)+ than…

     The grain output is 8 percent higher this year than that of last year.

     今年比去年糧食產(chǎn)量增加8%。

     d. 還可以用by+倍數(shù),表示增加多少倍

     The production of grain has been increased by four times this year.

     今年糧食產(chǎn)量增加了4倍。

    2)分?jǐn)?shù)表示法

    構(gòu)成:基數(shù)詞代表分子,序數(shù)詞代表分母。分子大于1時(shí),分子的序數(shù)詞用單數(shù),分母序數(shù)詞用復(fù)數(shù):

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