forty-five:forty-fifth
three:third
nine:ninth
thirty:thirtieth
two:second
five:fifth
twelve:twelfth
另外,比较级前要加the缩写形式基数词没有缩写，如果你要偷懒就直接写数字。序数词的缩写其实很简单，写上数字，再写上最后两个字母。例如45th,3rd,9th,30th,2nd,5th,12th,这种缩写方式在写日期时十分常用