Frequency of Occurrence of Letters in Spanish

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Frequency of Occurrence of Letters in Spanish

The following table and text are from:
Fletcher Pratt, Secret and Urgent: the Story of Codes and Ciphers Blue Ribbon Books, 1939, pp. 254-255.

Rank	Letter	Frequency of occurrence in 1000 words	Frequency of occurrence in 1000 letters
1	E	678	136.76
2	A	622	125.29
3	O	431	86.84
4	S	391	79.8
5	R	341	68.73
6	N	333	67.12
7	I	310	62.49
8	D	291	58.56
9	L	247	49.71
10	C	232	46.79
11	T	230	46.29
12	U	195	39.34
13	M	156	31.5
14	P	124	25.05
15	B	70	14.2
16	G	50	10.06
17	Y	44	8.95
18	V	44	8.95
19	Q	43	8.75
20	H	35	7.04
21	F	34	6.94
22	Z	26	5.23
23	J	22	4.43
24	X	11	2.21
25	W	1	.23
26	K	.5	.04

"The average length of Spanish words is 4.96 letters.

It will be noted that the letters, when arranged by relative frequency, fall into certain well-defined groups.

In short messages, any letter is likely to show a frequency higher than another letter of the same group.

For convenience' sake the groups may be listed as follows:

I	E, A
II	O, S
III	R, N, I, D
IV	L, C, T, U
V	M, P
VI	B, G, Y, V, Q, H, F, Z, J, X
VII	K, W

If the article "el" is omitted, L drops into the fifth group, and A shows a frequency higher than E.

In Spanish, samples of less than 500 words are very inadequate for determinations by use of frequency tables.

Even in samples of this length, A is quite apt to show a frequency higher than E, and C, D and P (which exhibit the sharpest variation from the frequencies given in the table) often rank directly after E in frequency.

Leading peculiarities by which Spanish may be identified from English (in transposition ciphers):

High frequency of Q
High frequency of A
Low frequency of T

Absence of K and W (which seldom occur in Spanish except in proper names of foreign origin).

Leading peculiarities by which Spanish may be identified from French:

High frequency of O
Low frequency of T
Low frequency of U

Doubled letters are very infrequent in Spanish."

Verified by: DT 3/99

Disclaimer:
While the Library has verified the information presented in these files in what it considers to be reliable and authoritative sources, it cannot take responsibility for nor guarantee the accuracy of the information presented.