1-20基数词和序数词英语序数词：
第bai1 first 1st 第2 second 2nd 第3 third 3rd
第4 fourth 4th 第5 fifth 5th 第6 sixth 6th
第7 seventh 7th 第8 eighth 8th 第9 ninth 9th
第10 tenth 10th 第11 eleventh 11th 第12 twelfth 12th
第13 thirteenth 13th 第14 fourteenth 14th 第15 fifteenth 15th
第16 sixteenth 16th 第17 seventeenth 17th 第18 eighteenth 18th
第19 nineteenth 19th 第20 twentieth 20th
1到20的英语序数词？1）序数词第一至第二十的数字为:
first (1st) second (2nd)third (3rd) fourth (4th) fifth (5th) sixth (6th) seventh (7th) eighth (8th) ninth (9th) tenth (10th) eleventh (11th) twelfth(12th) thirteenth (13th) fourteen (14th) fifteenth (15th) sixteenth (16th) seventeen (17th) eighteenth (18th) nineteenth (19th) twentieth (20th)
注：英语序数词第1-19除了first、 second、 third 有特殊形式外，其余均由基数词加后缀-th 构成。
序数词英语1到20变化规则从第一～第十九:one–first、two–second、three–third、five–fifth、eight–eighth、nine–ninth、twelve–twelfth为特殊形式外，其他的序数词都是由它的序数词加th构成。