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　　数词

　　一、基数词及其主要用法

　　表示数目的词称基数词。15 fifteen，几百几千不加s，242 two hundred and forty-two，5058 five thousand and fifty-eight，9，600，000 nine million six hundred thousand

　　1.基数词可以用于数字的计算。

　　6+8 = 14 Six plus eight is fourteen.

　　9-7 = 2 Nine minus seven is two.

　　7X5 = 35 Seven times five is thirty-five.

　　8÷4 = 2 Eight divided by four is two.

　　2.基数词可以表示人的大致年龄和年代。

　　He died in his fifties.

　　3.基数词可以用来表达年份、时间、电话号码。

　　1700 seventeen hundred

　　1814 eighteen fourteen

　　4.基数词可以用于编号。

　　Number six， line 4， page 19， Bus(No.) 332， Platform (No.) 5， Room 101

　　5.基数词可以和其他词一起构成合成形容词，在句子中作定语。

　　A one-month-old baby can recognize its mother by smell.

　　This eleven-month-old baby can speak a few words.

　　(The baby is eleven months old.)

　　The teacher asked us to write a four-thousand-word essay as our homework.

　　(There are four thousand words in the essay.)

　　二、序数词及其主要用法

　　表示顺序的词称为序数词。如first， second， third， fourth， ninth， twenty-first， forty-fifth等。

　　序数词可以用来表示日期和世纪。May the first / the first of May (5.1) ， August the eighth / the eighth of August (8.8) ， the twentieth century， the twenty-first century

　　序数词在句子中前面一般加the

　　The first of October is our National Day.

　　She was the third to arrive.

　　序数词在句子中前面加不定冠词，表示“再一”又一“。

　　They'll have to do it a second time.

　　Shall I ask him a third time?

　　When he sat down ， a fourth man rose to ask.

　　三、分数词的构成

　　分数的分子用基数词表示，分母用序数词表示，若分子大于1，分母需用复数。

　　two-thirds(2/3)，one-third(1/3)， nine-tenths (9/10)， five-twelfths(5/12)。

　　特殊表达法有：one half (1/2)，a quarter (1/4)， three quarters (3/4) .

　　考试重点

　　基数词可以和其他词一起构成合成形容词，在句子中作定语，名词不能加s.

　　数词部分需特别注意dozen， hundred， million， billion 等词。表示具体数字时，这些词用单数形式，表示不具体的数字时，须用dozens of， hundreds of 这类的结构。

　　I want three dozen of these.

　　He has been there dozens of times.

　　当数词与名词及其他词构成合成形容词时，合成形容词中间若用连字符，则其中的名词须用单数形式。

　　The homework for the next period is to write a two-hundred-word composition about your hometown.

　　Mary is a eleven-year-old girl.

　　(Mary is eleven years old.)