(一) 知识概要
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) 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. nine
B. the ninth
C. ninth
D. 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.
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