第31 序数词怎么写

thirty-first 或者 31st

规律：
one.first 1st
two.second 2nd
three.third 3rd
four.fourth 4th
five.fifth 5th
six.sixth 6th
seven.seventh 7th
eight.eighth 8th
nine.ninth 9th
ten.tenth 10th
eleven.eleventh 11th
twelve.twelfth 12th
thirteen.thirteenth 13th
fourteen.fourteenth 14th
fifteen.fifteenth 15th
sixteen.sixteenth 16th
seventeen.seventeenth 17th
eighteen.eighteenth 18th
nineteen.nineteenth 19th
twenty.twentieth 20th

twenty-one.twenty-first 21st
twenty-two.twenty-second 22nd
twenty-three.twenty-third 23rd
twenty-four.twenty-fourth 24th
twenty-five.twenty-fifth 25th

。。。。。 。。。。。。
以此类推
thirty-one.thirty-first 31th

31st,也可写为thirty-first

the thirty-first

thirty-first

the thirty-first

31st