关于英语里的序数词的写法

表示顺序的词称为序数词,one— first,two— second,three— third,five— fifth,eight—eighth,nine—ninth,twelve— twelfth等等
表示数目的词称为基数词,one two等等
构成分数的规则是分子基数词,分母序数词,分子大于一,分母加“s”.
所以上述eighty-sixth就错,应为eighty-sixths.
one third就正确