帮你学会一到二十一的基数词和序数词 基数词表示数目的多少，序数词表示事物的先后顺序。基数词（Cardinal Numbers）从一到二十一依次是：one, two ,three ,four, five ,six ,seven ,eight .nine .ten ,eleven , twelve, thirteen fourteen fifteen sixteen ,seventeen eighteen nineteen twenty ，twenty-one. 序数词（Ordinal Numbers）依次是：first, second, third, fourth , fifth , sixth seventh ,eighth ,ninth ,tenth, eleventh twelfth thirteenth fourteenth fifteenth sixteenth seventeenth eighteenth nineteenth twentieth twenty-first .一到二十一的基数词对应的序数词见下表： 基数词 one two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen twenty twenty-one 序数词 first second third fourth fifth sixth seventh eighth ninth tenth eleventh twelfth thirteenth fourteenth fifteenth sixteenth seventeenth eighteenth nineteenth twentieth twenty-first 序数词的缩写形式 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 20th 21st 基数词从一到二十一中，十三到十九均以”teen”结尾，十六，十七，十九，分别由six, seven, nine词尾加“teen”构成,”eight”以t结尾,加”een”变成十八。几十几用连字符链接,如twenty-one.序数词一般由基数词词尾加“th”构成。其中，第一，第二，第三，第五，第八，第九，第十二，第二十，第二十一除外。见下表： one two three five eight nine twenty twenty-one first second third fifth eighth ninth twentieth twenty-first 基数词几十均以“ty”结尾， 变序数词时，应改“y”为“i”加“eth”构成。第几十几，“几十”用基数词，“几”用序数词构成。 一到二十一的基数词和序数词用法实例： I．用所给词的适当形式填空。 1. Linda , you are the _______(one) student to come to school. You’re a good girl ! 2. In a foreign country ,they put their first names ______(one) , and put their last names last .In China , it’s opposite , instead . 3. September is the ________(nine) month of the year . 4. The _______(twelve ) month of the year is December . 5. Sunday is the ______(one) day of the week . 6. The building (楼房)has twelve floors . I’m on the _______(twelve ) 7. I’m 13 years old . Today is my ________(thirteen ) birthday . 8. What’ s seven and eight ? It’s _______(fifth). 9. The ________(twenty-one )paper(试卷) is mine .My name is on it . 10. Grace , I know the result(结果) of the English test .You are the ________(twenty ). And I’m the twenty-first. We both have to work harder ! 11. Monday is the ________（two）day of the week . 12. March is the _______(three )month of the year . 13. The ________(eight ) month of the year is August . 14. When is your birthday ? It’s on October _________(eighteen ) 15. Work comes ________(one) 参考答案：1.first 2.first 3.ninth 4.twelfth 5.first 6.twelfth 7.thirteenth 8.fifteen 9.twenty-first 10.twentieth 11.second 12.third 13.eighth 14.eighteen/eighteenth 15.first 练习详解：1题中.所给词前有定冠词the ,序数词前与the连用。基数词one的序数词是first。 2题中，外国人的名字先写， 姓氏后写。即put one’s first name first .因此答案是first 3题中，九月是一年中的第九个月，故应填第九， nine的序数词是ninth.注意：不是nineth. 4. December 是一年中的第十二个月。twelve的序数词是twelfth 即将twelve中的ve 改成f加th 构成。 5. 星期天（Sunday）是一周中的第一天。基数词one的序数词是first . 6. 这栋楼有十二（twelve）层（floors）,在第十二层，用序数词（twelfth） 7. 我十三岁，be+基数词表示年龄。今天是我的第十三个生日。用序数词。注意：序 数词前有形容词性物主代词时，序数词前不加定冠词the .形容词性物主代词和定冠词在英语中都是限定词，不重复使用。 8. 七加八等于十五，即fifteen . 9. 英语中，第几十几，第几十用基数词，几用序数词，第二十一即twenty-first. 10.英语中，第几十均以ty 结尾，变序数词时将y改成i 加eth构成。 11.Monday 是一周中的第二天。基数词two的序数词时second. 12.三月（March）是一年中的第三个月。基数词three的序数词是third. 13.August(八月）是一年中的第八个月。基数词eight以t结尾， 其序数词为eighth. 14.英语中，表示日期既可以写基数词，也可以写序数词。但均读序数词。 15.工作第一，故应填first。 本文来源：https://www.wddqw.com/doc/a1f92992bfeb19e8b8f67c1cfad6195f312be812.html