英语的序数词基本变法：
(1) 一般在基数词后加th,(2)-ve结尾的改为-fth,(3)-ty结尾的改为-tieth,(4)熟记特殊词。
2、序数词如下：
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th | ※first ※second ※third fourth fifth sixth seventh eighth ninth tenth eleventh twelfth | 13th 14th 15th 16th 17th 18th 19th | thirteenth fourteenth fifteenth sixteenth seventeenth eighteenth nineteenth | 20th 30th 40th 50th 60th 70th 80th 90th 100th | twentieth thirtieth fortieth fiftieth sixtieth seventieth eightieth ninetieth one undredth | 21st 22nd 23rd 35th 101st | twenty-first twenty-second twenty-third thirty-fifth one hundred and first |
1000th→one thousandth, 1000000th →one millionth., 第703→the seven hundred and third,
第5480→the five thousand four hundred and eightieth.
3、注：(1)两位以上的序数词仅个位数部分用序数词,其余部分仍用基数词。如：thirty-sixth,
(2) 使用序数词时一般加定冠词the. 如：I’m in the third grade.
(3) 序数词作几分之几”讲时,有复数形式。如：
1、/5→one fifth ; 2/3→ two thirds ; 4/7→ four sevenths ; 1/2→ a half ; 1/4→a quarter ; 3/4→ three quarters ; 50%→ fifty hundredths ( fifty per cent).
