Based on evidence from the billion-word Oxford English Corpus, Oxford have identified the hundred commonest English words found in writing globally:
1. the 2. be 3. to 4. of 5. and 6. a 7. in 8. that 9. have 10. I 11. it 12. for 13. not 14. on 15. with 16. he 17. as 18. you 19. do 20. at 21. this 22. but 23. his 24. by 25. from |
26. they 27. we 28. say 29. her 30. she 31. or 32. an 33. will 34. my 35. one 36. all 37. would 38. there 39. their 40. what 41. so 42. up 43. out 44. if 45. about 46. who 47. get 48. which 49. go 50. me |
51. when 52. make 53. can 54. like 55. time 56. no 57. just 58. him 59. know 60. take 61. person 62. into 63. year 64. your 65. good 66. some 67. could 68. them 69. see 70. other 71. than 72. then 73. now 74. look 75. only |
76. come 77. its 78. over 79. think 80. also 81. back 82. after 83. use 84. two 85. how 86. our 87. work 88. first 89. well 90. way 91. even 92. new 93. want 94. because 95. any 96. these 97. give 98. day 99. most 100. us |
Source: Concise Oxford English Dictionary (11th edition, 2006)
Note that these are the commonest words found in writing, which will not necessarily be the same as in speech.