The following shows the average frequency of common English words.
Such information is useful in data compression and security applications.
You should also look at the list of English letter frequency.

Total: 3,708,010 words of which 47,868 are different

1		3.28:	the
2		2.32:	and
3		1.86:	of
4		1.72:	to
5		1.57:	i
6		1.37:	a
7		0.98:	in
8		0.84:	that
9		0.77:	you
10		0.74:	it
11		0.69:	he		Wuthering Heights Bronte, Emily 1818 to 1848 Wildfell Bronte, Anne 1820 to 1849 Treasure Island Stevenson, Robert 1850 to 1894 Pygmalion Shaw, George Bernard 1856 to 1950 Poems Blake, William 1757 to 1827 Micrographia Hooke, Robert 1635 to 1703 Kim Kipling, Rudyard 1865 to 1936 Kidnapped Stevenson, Robert 1850 to 1894 Just So Stories Kipling, Rudyard 1865 to 1936 Jungle Book Kipling, Rudyard 1865 to 1936 Jane Eyre Bronte, Charlotte 1816 to 1855 Ivanhoe Scott, Walter 1771 to 1832 Economy of Mach and Manuf Babbage, Charles 1792 to 1871 Dracula Stoker, Bram 1847 to 1912 Complete Works Shakespeare, William 1564 to 1616 A Tale of Two Cities Dickens, Charles 1812 to 1870 39 Nine Steps Buchan, John 1875 to 1940
12		0.67:	my
13		0.61:	is
14		0.59:	his
15		0.57:	with
16		0.57:	for
17		0.54:	as
18		0.54:	not
19		0.51:	was
20		0.50:	me
21		0.49:	be
22		0.47:	but
23		0.39:	have
24		0.38:	this
25		0.35:	him
26		0.35:	by
27		0.35:	her
28		0.34:	on
29		0.33:	so
30		0.33:	at
31		0.31:	had
32		0.29:	all
33		0.29:	your
34		0.27:	or
35		0.27:	which
36		0.27:	will
37		0.26:	from
38		0.25:	are
39		0.25:	if
40		0.24:	no
41		0.24:	what
42		0.24:	she
43		0.23:	we
44		0.22:	they
45		0.20:	said
46		0.19:	do
47		0.19:	would
48		0.19:	thou
49		0.19:	were
50		0.19:	one
51		0.18:	there
52		0.18:	when
53		0.17:	now
54		0.17:	then
55		0.17:	them
56		0.17:	an
57		0.16:	more
58		0.16:	their
59		0.15:	shall
60		0.14:	well
61		0.14:	our
62		0.14:	out
63		0.14:	good
64		0.13:	thy
65		0.13:	like
66		0.13:	some
67		0.12:	up
68		0.12:	may
69		0.12:	come
70		0.12:	who
71		0.12:	very
72		0.12:	man
73		0.12:	than
74		0.12:	upon
75		0.11:	am
76		0.11:	been
77		0.11:	how
78		0.11:	such
79		0.11:	thee
80		0.11:	could
81		0.11:	here
82		0.11:	must
83		0.10:	sir
84		0.10:	time
85		0.10:	did
86		0.10:	know
87		0.10:	should
88		0.10:	into
89		0.10:	see
90		0.10:	go
91		0.10:	us
92		0.10:	these
93		0.09:	can
94		0.09:	any
95		0.09:	let
96		0.09:	lord
97		0.09:	little
98		0.09:	much
99		0.09:	other
100		0.09:	yet