十位以内:one- first,two- sencond,three- third要单记,
four,six,seven,ten,后加th,
five-fifth变ve为f再加th,eight- eighth共用t,nine-ninth去e加
th
11-19,基本加th,twelve- twelfth
20,30,40...整数变y 为 i 加eth,如:twenty- twentieth
带个位的数以个位为序数词,如:twenty- one twenty-first