Allograph

Allograph is a term in linguistics that refers to alternative forms of a letter of an alphabet or other graphemes, such as the capital letter (uppercase), small letter (lower case), italic, or various handwritten forms etc of the same letter in English alphabet.

In phonetics, allograph refers to letters or letter-combinations that represent a single phoneme, but written in different words, such as f and ph that represent the single sound in the words fake and phase respectively.