序数词：1.first,1st2.second,2nd3.third,3rd4.fourth,4th5.fifth,5th6.sixth,6th7.seventh,7th8.eighth,8th9.ninth,9th10.tenth,10th11.eleventh,11th12.twelfth,12th13.thirteenth,13h14.fourteenth,14th15.fiftee...