序数词口诀 序数词的口诀答:nineteenth.21-29的序数词:twenty-first, twenty-second, twenty-third, twenty-fourth, twenty-fifth, twenty-sixth, twenty-seventh, twenty-eighth, twenty-ninth.20-90整十的序数词:twentieth, thirtieth, fortieth, fiftieth, sixtieth, seventieth, eightieth, ninetieth.100序数词:one hundredth....