1. be：am/is/are → was/were

2. begin：begin → began → begun

3. break：break → broke → broken

4. bring：bring → brought → brought

5. build：build → built → built

6. buy：buy → bought → bought

7. choose：choose → chose → chosen

8. come：come → came → come

9. do：do → did → done

10. drink：drink → drank → drunk

11. drive：drive → drove → driven

12. eat：eat → ate → eaten

13. fall：fall → fell → fallen

14. feel：feel → felt → felt

15. find：find → found → found

16. fly：fly → flew → flown

17. forget：forget → forgot → forgotten

18. get：get → got → got

19. give：give → gave → given

20. go：go → went → gone

21. grow：grow → grew → grown

22. have：have → had → had

23. hear：hear → heard → heard

24. hold：hold → held → held

25. hope：hope → hoped → hoped

26. know：know → knew → known

27. lay：lay → laid → laid

28. leave：leave → left → left

29. lose：lose → lost → lost

30. make：make → made → made

31. meet：meet → met → met

32. pay：pay → paid → paid

33. put：put → put → put

34. read：read → read → read

35. ride：ride → rode → ridden

36. run：run → ran → run

37. say：say → said → said

38. see：see → saw → seen

39. sell：sell → sold → sold

40. send：send → sent → sent

41. show：show → showed → shown

42. sing：sing → sang → sung

43. sit：sit → sat → sat

44. sleep：sleep → slept → slept

45. speak：speak → spoke → spoken

46. spend：spend → spent → spent

47. stand：stand → stood → stood

48. take：take → took → taken

49. teach：teach → taught → taught

50. see：see → saw → seen

记住这些不规则动词的过去式对于英语学习者来说非常重要。在实际应用中，这些动词的过去式和过去分词形式在构成时态、被动语态和完成时等方面都起着关键作用。掌握不规则动词的变化规律是提高英语水平的关键之一。