基数词 one eleven twenty-one two twelve twenty-two three thirteen thirty four fourteen forty five fifteen fifty six sixteen sixty seven seventeen seventy eight eighteen eighty nine nineteen ninety ten twenty ninety-nine 基数词变序数词的规则 1. 特殊变化1 2 3 5 9 12 8 2. 20以上，个位不是零的数字，只变个位，其余不变 如：twenty-one 变为twenty-first 3. 以ty结尾的，变y为i，再加eth 如：twenty变为twentieth 4. 其它情况直接加th 序数词 first eleventh twenty-first second twelfth twenty-second third thirteenth thirtieth fourth fourteenth fortieth fifth fifteenth fiftieth sixth sixteenth sixtieth seventh seventeenth seventieth eighth eighteenth eightieth ninth nineteenth ninetieth tenth twentieth ninety-ninth 本文来源：https://www.wddqw.com/doc/952ebe3d8ad63186bceb19e8b8f67c1cfbd6eeb5.html