一、基数词的构成和用法
(一)构成
1.1-12特殊记,即one,two,three,four,five,six,seven,eight,nine,ten,eleven,twelve没有规律。
2.13-19以teen结尾,这是基数词的其中一个后缀,注意13是thirteen,15是fifteen,18是eighteen.
3.20-90(即整十)以ty结尾,这是基数词的一个后缀,注意40是forty,50是fifty,80是eighty.
4.21-99即表示“几十几”,分成由“几十”+“几”,实际上是由以上的“3”加“1”构成,注意中间加一个连字符。例如:21是twenty-one,99是ninety-nine.5,678读作:five thousand,six hundred and seventy-eight,1,213,2,56读作:one million,two hundred and thirteen thousand,two hundred and fifty-six,2,143,456,789读作:two billion,one hundred and forty-three million,four hundred and fifty-six thousand,seven hundred and eighty-nine.
5.101-999的百位数由hundred加and再加两位数或个位数,例如:311读作:three hundred and eleven,745读作:seven hundred and forty-five,805读作:eight hundred and five.
6.四位数以上(含四位数)的数字从右向左每三位加一个逗号,第一、第二、第三个逗号的位置分别读thousand,million,billion.
综上所述不难发现:个位数的表达用第一点,两位数的表达用第二到第四点,百位数的表达用第五点,千位以上(含千位)的数字主要用第六点。
7.在表达确切数字时不用复数形式,即基数词与"s"势不两立,例如:two hundred students不能说成two hundreds students.在表示不确切的数字时,用复数形式且后面要用of,即"s“与”of"形影不离。例如:hundreds of students 不能说hundred of students.有时也可加上several,a few等词表示不确切的数量,例如:several thousand times,a few billion years.
(二)用法
1.表示“在几十世纪的几十年代”用“in+the+逢+的数词的复数”,例如:in the 1880s.
2.表示在某人几十多岁时用“in one’s +数词的复数”,例如:in my twenties,in his thirties.
3.在与基数词合成的定语即在复合形容词中,名词用单数,例如:an eight-month-old baby,the boys’ 800-meter race
4.基数词在句中可以用作主语、宾语、表语、同位语、定语等,例如:Eight is a lucky number in eastern countries.(作主语)
They need one billion altogether.(作宾语)
Five and three is eight.(作表语)
You two are both good students.(作同位语)
I have two bikes.(作定语)
二、序数词的构成和用法
(一)构成
1.通常在基数词后面加上后缀-th构成(第五是fifth,第八是eighth,第九是ninth),例如:four—fourth.
2.first(第一),second(第二),third(第三)特殊记。
3.表示第几十的序数词由相应的基数词词尾的y变i,再加eth.例如:twenty—twentieth,ninety—ninetieth.
4.表示第几十几的序数词,只要把相应基数词的末位数变成序数词表达即可,而前面其他仍用基数词。例如:twenty-one→twenty-first.
5.100以上的序数词,第100表示为100th(读作one hundredth),第101表示为101st(读作one hundred and first),其他的情况类推。
6.序数词的缩写形式:数字+序数词最后两个字母,例如:first—1st,fourth—4th,ninety-eighth—98th.
(二)用法
1.用作主语,例如:The first is better than the second.
2.用作宾语,例如:At last,he choose the third.
3.用作定语,序数词前用定冠词the,例如:It is the fourth time that you have been late for school in one month.
4.用作表语,例如:Li Ping was the second in the exam.
5.表示“又一、再一”,不强调按照一定规律排列的先后顺序时用不定冠词,例如:She lit three matches. Then she lit a fourth match. You will be the second to speak.(你第二个发言。)You have to speak a second time.(你必须再一次发言。)
6.表示编号,名词+基数词或the+序数词+名词,即用基数词时,前面不加定冠词,基数词后置;用序数词时,前面要加定冠词,且名词要后置。例如:Lesson One=the First Lesson,Part Two=the Second Part
7.用于固定搭配中,例如:at first,first of all.
三、分数、小数、百分数的构成和用法
(一)分数的构成和用法。分数由基数词和序数词构成,分子用基数词,分母用序数词,分子大于一时,分母的序数词用复数形式。例如:1/5—one(a)fifth,3/5—three fifths,1/3— one third,1/2—a half,1/4—a quarter.
分数作主语时,谓语动词与分数所表示的名词一致。例如:One third students are from China.
(二)小数点读point,零读/?藜u/或zero,小数点前面的基数词与前面所讲的基数词的读法一样,小数点后的数字要一一读出。例如:0.3—zero point three,6.31—six point three one.
(三)百分数由percent表示,当名词用复数时,不变化。例如:11%—11 percent,Fifteen percent of the papers are written in Chinese.