1-20序数词

从第一到第二十的序数词为：

1.first 2.second 3.third 4.fourth 5.fifth 6.sixth 7.seventh 8.eighth 9.ninth 10.tenth 11.eleventh 12.twelfth 13.thirteenth 14.fourteenth 15.fifteenth 16.sixteenth 17.seventeenth 18.eighteenth 19.nineteenth 20.twentieth。