1. first 1st

2. second 2nd

3. third 3rd

4. fourth 4th

5. fifth 5th

6. sixth 6th

7. seventh 7th

8. eighth 8th

9. ninth 9th

10. tenth 10th

11. eleventh 11th

12. twelfth 12th

13. thirteenth 13th

14. fourteenth 14th

15. fifteenth 15th

16. sixteenth 16th

17. seventeenth 17th

18. eighteenth 18th

19. nineteenth 19th

20. twentieth 20th

21. twenty-first 21st

22. twenty-second 22nd

23. twenty-third 23rd

24. twenty-fourth 24th

25. twenty-fifth 25th

26. twenty-sixth 26th

27. twenty-seventh 27th

28. twenty-eighth 28th

29. twenty-ninth 29th

30. thirtieth 30th

31. thirty-first 31st

32. thirty-second 32nd

33. thirty-third 33rd

34. thirty-fourth 34th

35. thirty-fifth 35th

36. thirty-sixth 36th

37. thirty-seventh 37th

38. thirty-eighth 38th

39. thirty-ninth 39th

40. fortieth 40th

建议：在正式场合或需要准确表达的情况下，建议使用完整的序数词，以避免混淆和误解。