序數詞依次如下：

1st=first

2nd=second

3rd=third

4th=fourth

5th=fifth

6th=sixth

7th=seventh

8th=eighth

9th=ninth

10th=tenth

11th=eleventh

12th=twelfth

13th=thirteenth

14th=fourteenth

15th=fifteenth

16th=sixteenth

17th=seventeenth

18th=eighteenth

19th=nineteenth

20th=twentieth

21st=twenty-first

22nd=twenty-second

23rd=twenty-third

24th=twenty-fourth

25th=twenty-fifth

26th=twenty-sixth

27th=twenty-seventh

28th=twenty-eighth

29th=twenty-ninth

30th=thirtieth