推荐阅读：
数词用来表示人或物的数目多少和顺序。所以数词主要有两种：基数词，用于计数，如：one, two…而序数词用于表示位置先后或次序，台：first second…其构成法如下：
阿拉伯数字 基数词 序数词 简写序数词
1 one first 1st
2 two second 2nd
3 three third 3rd
4 four fourth 4th
5 five fifth 5th
6 six sixth 6th
7 seven seventh 7th
8 eight eighth 8th
9 nine ninth 9th
10 ten tenth 10th
11 eleven eleventh 11th
12 twelve twelfth 12th
13 thirteen thirteenth 13th
14 fourteen fourteenth 14th
15 fifteen fifteenth 15th
16 sixteen sixteenth 16th
17 seventeen seventeenth 17th
18 eighteen eighteenth 18yh
19 nineteen nineteenth 19th
20 twenty twentieth 20th
21 twenty-one twenty-first 21st
30 thirty thirtieth 30th
40 forty fortieth 40th
50 fifty fiftieth 50th
60 sixty sixtieth 60th
70 seventy seventieth 70th
80 eighty eightieth 80th
90 ninety ninetieth 90th
100 a(one)hundred hundredth 100th
104 one hundred and four hundred and fourth 104th
1000 a(one) thounsand thounsandth 1000th
10000 ten thounsand ten thounsandth 10000th
1000000 one million millionth 1000000th
基数词与序数词都有一定的构成方法，但都有特殊例外的几个字，所以除了要学会一般构成法之外，还要特别记熟一些例外。因它们在考试中出现的频率很高。
1 基数词构成结构
21～99的两位数字，在10位和个位之间加连字符构成，如89-eighty-nine.101～999的三位数字，由hundred 加and 再加二位数或未位数字，如： 101-one hundred and one, 223-two hundred and twenty-three.四位以上数字，应从个位起向前数三位加逗号，读作thousand,再数三位加第二个逗号，读作million,再数三位加逗号，读作billion，其读法如下：
1001-one thousand and one5386-five thousand, three hundred and eighty-six要注意的是hundred, thousand, million与billion的用法。①前面有别的基数词时，即若干个百、千、百万、十亿时，其本身都不要加s，如：three hundred students。 ② 若表示成百，成千或数百，数千时，前面不能有基数词，但其本身要用复数形式，然后+of+名词复数。如：thousands and thousands of。 (成千上万)
2 序数词的构成法
序数词除first, second, third 以外，其余一般在词尾加th构成，除一般略有差异的各别数词外，很容易掌握。其二位数或多位数只将后面的个位数字改为序数词，其前面各位数字均不改变，都用基数词。
3 其他数字表示法
小数的小数点读作point，零读作o[u]或zero,小数点后面的数字按个位基数词依次读出。分数分子用基数词，分母用序数词，当分子大于1时，分数要在序数词上加s，但1/2用one half, 1 4 用a quarter. 1 3 读作one third而 2 3 读作two thirds。百分数(%)，读作per cent (percent),但不论是多少均用作单数形式不能加s。表示日期有两种说法和四种写法，如：2月1号英语表达法为：the first of February而美语为February (the) first,但其书写上可有四种写法① February 1 ② February 1st ③ 1st February ④ 1/2。倍数的讲法有所不同。两倍用twice,而三倍以上用序数词加times,如：He has three times as many books as I have.
(二) 正误辨析
[误] 1107 should be read as a thousand a hundred as seven.
[正] 1107 should be read as one thousand one hundred and seven.
[析] 在读数字时，如：and前只有百或千时，用one hundred/ one thousand 还是a hundred /a thousand全是可以的。但如果文有百又有千时，则只能用one不要用a。 如果没有and时，如：1100也只能读作one thousand one hundred 或eleven hundred.
[误] I drove about half mile.
[正] I drove about half a mile.
[析] 半小时为half an hour, 半天为half a day, 半镑为half a pound, 尽量避免用half a year, half a month, 要用six months, two weeks 或 fifteen days 要注意的是Half of the work is done Half of the books are sold. 当Half 作名词时，其谓语动词要看of后面的名词而定。如名词是不可数名词则用单数谓语动词，如是复数名词时，则要用复数谓语动词。要注意的是一个半的表达法，如：One and a half apples is left on the table.其名词要用复数，但谓语动词则要用单数。
[误] 60 students are playing on the ground.
[正] Sixty students are playing on the ground.
[析] 在句首的数字要用文字而不要用阿拉伯数字，如数字过大则应放于句中，用阿拉伯数字。如： There are 166 students playing on the ground.
[误] He became famous around fifty years old.
[正] He became famous in his fifties.
[析] in his fifties 50多岁时，而in the fiflies 在50年代。
[误] There are about two thousands workers in our factory.
[正] There are about two thousand workers in our factory
[析] 几千，几百的表达法是基数词加thousand或加hundred,而且均不要加s。这样的单位还有dozen(打)， score (20年)等。
[误] In the morning there are hundred of old people walking in the park.
[正] In the morning there are hundreds of old people walking in the park.
[析] 当表达数百，数千时，要用hundreds of和thousands of 这一结构。
[误] The class begins at eight a. m.
[正] The class begins at 8 a. m.
[析] 与符号或与缩写的字母连用时一定要用数字，如：43%， 67, No.2…
[误] Twofifth of the books are sold out.
[正] Twofifths of the books are sold out.
[析] 分数表示法，分子用基数词，分母用序数词，但分子大于1时，分母要在序数词后加s。
[误] Tom was born on July eighteen.
[正] Tom was born on July eighteenth.
[析] 月日的表达法有美语和英语两种。 美语 July 18 读作 July eighteenth 英语 July 18th 读作 July the eighteenth
[误] I'll go to school at 7∶30 a. m. in the morning.
[正] I'll go to school at 7∶30 a. m/ at 7∶30 in the morning.
[析] a. m 即表达在早上之意，不要再用in the morning.
[误] The film will begin at three quarters past one.
[正] The film will begin at one quarter to two.
[析] 大于30分钟时不要使用past，而要用差多少不到几点的to来表达。
[误] Three time three is nine.
[正] Three times three is nine.
[析] times 此处作为"乘"讲一定要加s。 英语中乘除法表达式如下：
算法 种类 例 句
加法 一般 Five and six is eleven.
正式 Five plus six is (equals) eleven.
减法 一般 Eight take away four leaves (is) four.
Four from Eight leaves (is) four.
正式 Eight minus four equals (is) four.
乘法 一般 Three fours are twelve 3×4=12
正式 Three times four equals (is) twelve.
一般 Two in to four is two.
正式 Four pided by two equals two.
(三) 例题解析
1 - How many students are there in your school, Mike?
- There are over ___ students in our school.
A. two thousands B. two thousands of
C. two thousand D. two thousand of
[答案] C.
[析] 有基数词在前面时thousand， hundred 等词不能加s，也不能加of结构，只有在thousands of时才可以使用。
2 John lives on ___ floor. He doesn't use a lift to go up and down.
A. nineB. the ninthC. ninthD. a ninth
[答案] B.
[析] 序数词前加定冠词，nine 与 ninth 的拼写上有一个e字母相差别。
3 Wu Dong won the girls' ___ race in the school sports meeting last week.
A. 100 metresB. 100metresC. 100 metreD. 100metre
[答案] D.
[析] 数词、名词、形容词等词用连字符连接成的形容词中，名词都不要加s，如： I have to write a twothousandword report.而且由连字符组成的形容词只能放于名词前，不能放于名词后，作后置定语，或用在be动词后作表语。
4 There are ___ students in our school.
A. four hundred twentyB. four hundred and twenty
C. four hundreds twentyD. four hundreds and twenty
[答案] B.
5 - How many days are there in a year?
- There are ___ .
A. three hundreds and sixtyfive
B. three hundreds sixtyfive
C. three hundred and sixtyfive
D. three hundred sixty five
[答案] C.
6 We have learned about ___ English words.
A. nine hundreds B. nine hundred
C. nine hundred of D. nine hundreds of
[答案] B.
7 Autumn is ___ season of the year.
A. thirdB. the threeC. thirdsD. the third
[答案] D.
8 They are learning ___ now.
A. Lesson EightB. the eight lesson
C. Lesson EiththD. Eighth lesson
[答案] A.
[析] 第几课，第几个门……，在英语中有两种说法，①Lesson Two, Gate Two但要注意每一单词的首字母要大写。② the second lesson, the second gate 首字母不要大写，并要注意有些缩写的读法。如:
p. 8-第8页(page eight)
$ 8.50-8.5美元(five dollars and fifty)
电话号码66164532-(six, six, one, six, four five, three, two)
9 The boy was so hungry that he ate ___ .
A. three bowls of rices B. three bowl of rice
C. three bowl of rices D. three bowls of rice
[答案] D.
[析] rice 是不可数物质名词，而bowl是可数名词。
10 There are ___ months in a year.
A. twelve B. twelf C. twelveth D. twelfth
[答案] A.
