1至50的基数词和序数词

基数词：

1. One

2. Two

3. Three

4. Four

5. Five

6. Six

7. Seven

8. Eight

9. Nine

10. Ten

11. Eleven

12. Twelve

13. Thirteen

14. Fourteen

15. Fifteen

16. Sixteen

17. Seventeen

18. Eighteen

19. Nineteen

20. Twenty

21. Twenty-one

22. Twenty-two

23. Twenty-three

24. Twenty-four

25. Twenty-five

26. Twenty-six

27. Twenty-seven

28. Twenty-eight

29. Twenty-nine

30. Thirty

31. Thirty-one

32. Thirty-two

33. Thirty-three

34. Thirty-four

35. Thirty-five

36. Thirty-six

37. Thirty-seven

38. Thirty-eight

39. Thirty-nine

40. Forty

41. Forty-one

42. Forty-two

43. Forty-three

44. Forty-four

45. Forty-five

46. Forty-six

47. Forty-seven

48. Forty-eight

49. Forty-nine

50. Fifty

序数词：

1. First

2. Second

3. Third

4. Fourth

5. Fifth

6. Sixth

7. Seventh

8. Eighth

9. Ninth

10. Tenth

11. Eleventh

12. Twelfth

13. Thirteenth

14. Fourteenth

15. Fifteenth

16. Sixteenth

17. Seventeenth

18. Eighteenth

19. Nineteenth

20. Twentieth

21. Twenty-first

22. Twenty-second

23. Twenty-third

24. Twenty-fourth

25. Twenty-fifth

26. Twenty-sixth

27. Twenty-seventh

28. Twenty-eighth

29. Twenty-ninth

30. Thirtieth

31. Thirty-first

32. Thirty-second

33. Thirty-third

34. Thirty-fourth

35. Thirty-fifth

36. Thirty-sixth

37. Thirty-seventh

38. Thirty-eighth

39. Thirty-ninth

40. Fortieth

41. Forty-first

42. Forty-second

43. Forty-third

44. Forty-fourth

45. Forty-fifth

46. Forty-sixth

47. Forty-seventh

48. Forty-eighth

49. Forty-ninth

50. Fiftieth

基数词解释：

基数词是对集合进行分类的一种方式，将互相对等的集合划入同一类。每个集合都被分配到某一类中。集合A所属的类称为集合A的基数，记作|A|（或cardA)。当集合A和B属于同一类时，它们具有相同的基数，即|A|=|B|。反之，如果A和B不属于同一类，它们的基数则不同。如果将单元素集的基数记作1、两个元素的集合的基数记作2、依此类推，那么任何有限集的基数都与传统意义上的自然数一致。空集的基数也记作0。因此，有限集的基数就是传统概念下的“个数”。然而，对于无穷集，传统概念中没有个数，但根据基数概念，无穷集也有基数。例如，任何可数集（也称可列集）与自然数集N具有相同的基数，即所有可数集是等基数集。不仅如此，还可以证明实数集R与可数集的基数不同。所以，集合的基数是个数概念的推广。