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.