The alphabet is a set of letters that make words that are used to represent the basic sounds or the written structure of a language. The word “alphabet” comes from the first two letters of the Greek alphabet, alpha, and beta.
The English alphabet has twenty-six (26) letters and fifty-two (52) letters if you count the twenty-six uppercase (26) and twenty-six (26) lowercase, which is represented by the following graphemes: Aa, Bb, Cc, Dd, Ee, Ff, Gg, Hh, Ii, Jj, Kk, Ll, Mm, Nn, Oo, Pp, Qq, Rr, Ss, Tt, Uu, Vv, Ww, Xx, Yy, Zz. In most languages written in Latin script (including English) these twenty-six (26) symbols represent consonants and vowels.
Some consider that there are no upper- or lower-case letter forms for these graphemes and that all are considered equal. That may be true, but visually and conceptually there is a difference especially if one uses certain cases for emphasis and rules.
However, some languages use additional diacritics to modify specific phonemes represented by graphemes.
See Dictionary and Lexicon