六、数词
（一）基数词 在英语中表示数目的词称为基数词。
1.基数词的构成
（1）1-20
one,two,three,four,five,six,seven,eight,nine,ten,eleven,twelve,thirteen,fourteen,fifteen,
sixteen,seventeen,eighteen,nineteen,twenty
（2）21-99 先说“几十”，再说“几”，中间加连字符。
23→twenty-three,34→thirty-four,45→forty—five,56→fifty-six,67→sixty-seven,78→seventy-eight,89→eighty-nine,91→ninety-one
（3）101—999先说“几百”，再加and,再加末两位数或末位数；
586→five hundred and eighty-six,803→eight hundred and three
（4）l,000以上,先从右往左数，每三位数加一个“,”,第一个“,”前为thousand.第二个“,”前为
million,第三个“,”前为billion（美式）或thousand ,million（英式）,然后一节一节地表示。
1,001→one thousand and one
9,785→nine thousand, seven hundred and eighty-five
18,423→eighteen thousand,four hundred and twenty-three
6,260,309→six million two hundred and sixty thousand three hundred and nine
750,000,000,000→seven hundred and fifty, billion（美式） seven hundred and fifty thousand million（英式）
2.基数词的用法
（1）作主语
eg.Four Of them come from Paris.
（2）作宾语
eg.一 How many books would you like？
一I would like two.
（3）作表语
eg.Seven minus two is five.
（4）作定语
eg.There are three people in my family·
（5）作同位语
eg. You two will go swimming with us.
（6）表具体数字时,hundred,thousand,million用单数。
eg. There are six hundred students in our grade.
（7）表不确定的数字时,数词用复数。若带名词，再加of hundreds of（数百,成百上千的）,thousands of（数干,成千上万的）,millions of（数百万）
eg,They arrived in two sand threes.他们三三两两地来了。
（8）表示“…十”的数词的复数可以表示人的岁数或年代。
eg. He is in his early thirties.他有三十来岁（31—34岁）：
This took place in the 1930s.这事发生在二十世纪三十年代；
（9）表示时刻
eg.I watch CCTV News at seven o’clock every evening.
（二）序数词 在英语中表示顺序、次序的词称为序数词。
1.序数词的构成
（1）一般在基数词后加th
eg.four→fourth,thirteen→thirteenth
（2）不规则变化
one→first,two→second,three→third,five→fifth,eight→eighth,nine→ninth,twelve——~twelfih
（3）以y结尾的十位整数，变y为ie再加th
twenty→twentieth, forty→fortieth, ninety→ninetieth
（4）从二十一后的“几十几”直至“几百几十几”或“几千几百几十几”只将个位的基数词变为序数词。
twenty-first,two hundred and forty-fifth
2.序数词的用法
（1）序数词作定语时，一般要与定冠词或物主代词连用。
eg.Tom is their second son.
He is the first one to come here.
（2）序数词有时可与不定冠词连用，表示数量上“又—”,“再一”
eg： He tried a second time.他又试了—次。
Shall l ask him a third time？还要我再问他—次吗？我已问了他两次）
（3）序数词的缩写形式为：阿拉伯数字加上这个词的末尾两个字母。
1st 2nd,3rd,4th,20th,21st,22nd,23rd
（4表示年、月、日时，年用基数词，日用序数词。
2005年8月15日：（英）15,8,2005=15th,August,2005；（美）8,15,2005=August 15th,2005
（三）基数词和序数词都可以用来给数字编号。
No.1（1号）,No.3bus（3路公共汽车）,Room 103,（103号旁间）
The first lesson=Lesson Two（第二课）
（四）分数词的表达
分子用基数词，分母用序数词，分子大于1时，分母加s
eg.1／3-one third；2／5-two fifths
（五）数学运算的表达
eg.3 5=8 Three plus／and five is eight.
9-2=7 Nine minus two is seven.
6x5=30 Five times six is thirty ／six unutilized five is thirty.
8÷2=4 Eight divided by two is four.
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