An alphabet is a standard set of letters—basic written symbols or graphemes—each of which represents a phoneme in a spoken language, either as it exists now or as it was in the past. There are other systems, such as logographies, in which each character represents a word, morpheme, or semantic unit, and syllabaries, in which each character represents a syllable. Alphabets are classified according to how they indicate vowels:

 This depends, to a great extent, on the sample size and the type of text that is analyzed. Here is one result:

e t a o i n s r h l d c u m f p g w y b v k x j q z
 
General Letter Frequencies
e 0.124167
t 0.0969225
a 0.0820011
i 0.0768052
n 0.0764055
o 0.0714095
s 0.0706768
r 0.0668132
l 0.0448308
d 0.0363709
h 0.0350386
c 0.0344391
u 0.028777
m 0.0281775
f 0.0235145
p 0.0203171
y 0.0189182
g 0.0181188
w 0.0135225
v 0.0124567
b 0.0106581
k 0.00393019
x 0.00219824
j 0.0019984
q 0.0009325
z 0.000599