English as an Additional Language/The English alphabet
Note: if the target audience's native language already uses the Latin alphabet, then much of this information can be omitted.
English is written with the Latin alphabet. It consists of 26 letters:
lower-case letters: 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
upper-case letters: 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
Each letter has a lower-case and an upper-case (or "capital") form. In some cases (e.g. the letters S, X, and O), the upper-case form is simply a larger version of the lower-case. However, some letters have differing forms in upper- and lower-case, such as A, Q, and T.
Lower-case letters evolved from modified forms of the upper-case letters, which were used in ancient times.
Vowels and Consonants
There are 5 vowel letters in English: a, e, i, o, u ("y" and "w" also act as vowels, and are used for orthographic reasons). This does not correlate with the number of vowel sounds, of which there are about 14, depending on dialect.
There are 21 consonant letters: b, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w, x, y, z.
In many cases, the spelling of an English word only gives a rough indication of its pronunciation. For this reason, the English spelling system is notorious for being one of the hardest to learn of all the alphabetic scripts.