1.基數詞變序數詞。其規律爲：
1,2,3特殊記，加th從4起 (first,second,third,fourth)
8少t，9去e，千萬別忘記 (eighth,ninth) 逢5逢12，ve變f (fifth,twelfth)
20到90，y要變ie (twentieth,ninetieth) 若是幾十幾，前基後序別倒位 (ninety-first)
2.序數詞常與定冠詞the 連用。
練習:
①Henry has learned eight _________ French words this year.
red reds red of reds of
②The _________lesson is the most difficult one in Book Two. (twenty)
