英语中，用来表示事物的数目的词是基数词，用来表示事物顺序的词是序数词。那么基数词变序数的口诀是什么呢？

记住："基变序有规律，结尾字母是th"，"一、二、三特殊记，结尾字母t,d,d","八去t，九去e,f要把ve替"，"ty将y变成i,th前面有个e","几十几，也好记，只变个位就可以"。

注意：在基数词改为序数词时，多数都在基数词尾加th，但one,too,three所对应的序数词依次为first,second和third（即"结尾字母t,d,d"）。eight在加th时要去掉末尾字母t(eight→eighth，即"八去t"）；nine在加th时要去掉字母e（nine→ninth,即"九去e")；以ve结尾在加th时，应先把ve用f换掉，然后再加th。（如：five→fifth,twelve→twelfth,即f要把ve替）；以ty结尾的基数词在变成序数词，应先将y变i，th前面还要加上字母e（如：twenty→twentieth,thirty→thirtieth,......ninety→ninetieth等，即ty把y变成i，th前面还有一个e）；类似twenty-four,twenty-six这样"几十几"的基数词在改为序数词时，只需变个位就可以了。如：twenty-four→twenty-fourth,twenty-six→twenty-sixth等。

三．典型例解

( )1.Tom and Ann stood in front of the mirror and looked at ________.

A. her B. him C. them D. themselves

分析：D 本题考查反身代词的运用。依据题意：汤姆和安站在镜子前，看着他们自己。需要用反身代词，故用D。

（ ）2．September 10th is ___________.

A. Women's Day B. Children's Day C. Mid-autumn Day D. Teachers' Day

分析：D。本题考查节日名称。 本题属于社会常识。

（ ）3．Have you learned ____ lesson?

A. twelve B. twelveth C. the twelfth D. the twelve

分析：C。本题考查序数词的用法。题意为：你们学第十二课了吗？以ve结尾在加th时，应先把ve用f换掉，然后再加th。

( )4.-Who's the girl in red?

-Sorry, I don't know ____.

-____ is a new student.

A. she; She B. her; She C. her; Her D. she; Her

分析：B 前者在动词后面做宾语应用宾格her, 后者在句子中做主语应用主格she。

( )5.-Where does he live?

-He ____ in Shanghai.

A. lives B. live C. is live D. to live

分析：A 从第一句可以判定下句用一般现在时, 答句主语为第三人称单数, 故选A。

( )6.Li Lei often ____ Lin Tao ____ his English.

A. help; to B. helps; with C. helps; to D. help; with

分析：B help sb. with sth. 意为"帮助某人做某事", 与help sb. (to) do sth. 同义。题干中often暗示用一般现在时, 主语为第三人称单数, 故选B。

( )7.He doesn't like apples ____.

A. very B. much C. at all D. little

分析：C not ... at all 表示"一点也不"，故选C。

( )8.I like the little cat a lot but she likes it ____.

A. a lot B. a little C. lot D. muchX_X_K]