第九：ninth；第十九：nineteenth；第二十九：twenty-ninth
序数词除了不规则的first,second,third,fifth外,其它的都是在后面直接加th,如fourth,sixth;
第几十几的就在后面的数加th,如twenty-fouth,thirty-sixth,seventy-ninth.
第九：ninth；第十九：nineteenth；第二十九：twenty-ninth
序数词除了不规则的first,second,third,fifth外,其它的都是在后面直接加th,如fourth,sixth;
第几十几的就在后面的数加th,如twenty-fouth,thirty-sixth,seventy-ninth.