碗碗小公主
序数词的构成分为四种。〔第一种〕1~3 有不同于基数词的形式*first (1st)*second (2nd)*third (3rd)〔第二种〕4 ~19 以及 100 是在基数词的基础上加后缀 -th,其中以下四个的词形与基数词略有变不同:*forth (4th)*fifth (5th)*eighth (8th)*ninth (9th)*hundredth (100th)〔第三种〕以 y 结尾的 20, 30, ..., 90,先把 y 改为 i 再加 -eth,如:*twentieth (20th)*fiftieth (50th)*ninetieth (90th)〔第四种〕“第几十几” 只把后面的基数词变为序数词即可,如:*twenty-first (21th)*thirty-second (32nd)*forty-third (43rd)*fifty-forth (54th)注意:序数词前都需要加定冠词 the。