1onefirst2twosecond3threethird4fourforth5fivefifth6sixsixth7sevenseventh8eighteighth9nineninth10tententh11eleveneleventh12twelvetwelveth13thirteen14fourteen15fifteen16sixteen17seventeen18eighteen19ninteen13~19的序数词都是基数词直接加th20twentytwentieth往后，二十几就是twenty加上几，比如23就是twenty-three，序数词twenty-third，其基数词和序数词形式跟前面一样。30thirtythirtieth40fourtyfourtieth50fiftyfiftieth60sixtysixtieth70seventyseventieth80eightyeightieth90nintynintieth100onehundredonehundreth。