Word for "only letters" [closed]

I am looking for a word that means "only letters A–Z", sort of like alphanumeric, but not numbers. The closest I got is alphabetic/alphabetical. The context is

Please enter a [word] string:

This is in a program I am making that doesn't work if anything other than A–Z is entered.

Solution 1:

While the word you are looking for is indeed alphabetical, the only characters you allow are all letters — this excludes numbers, spaces, punctuation and special symbols like &.

Please enter only letters.

You could make it absolutely explicit with

Please enter only alphabetical letters.

Note that some languages include special characters like ß é ð and so on, which some users may well include in the definition of letter or alphabetical. You may need to exclude those explicitly too:

Please enter only unaccented alphabetical letters, A–Z or a–z.

Solution 2:

An alphabet is a standard set of letters . A true alphabet has letters for the vowels of a language as well as the consonants. The English language, which has 26 letters as goes like this; a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z.

In the program, for validation message, you can write :

Please enter an alphabetical string.

Allow only Alphabets in Textbox.

Please enter only alphabets.

Please input alphabet characters only.

Please enter alphabetical characters.