allograph

An allograph is a variant glyph that represents the same grapheme or phoneme as another glyph. The term is used in linguistics and typography to discuss writing variants of a sound or character. It covers letter shapes in different fonts or scripts and contextual forms in non-Latin scripts.

In phonology and orthography, a given phoneme may be written with multiple allographs. Examples: the /k/ sound can be written as c (as in cat), k (as in kite), or ck (as in back); the /f/ sound can be written as f (fun), ph (phone), or ff (coffee); the /s/ sound can be written as s, or c before e/i/y (cent), or sc before e/i (science). In non-Latin scripts, letter shapes can vary by position, as in Arabic, where letters change shape depending on context; in Greek, the sigma has two allographs: σ and ς.

Grapheme vs allograph: a grapheme is the abstract unit representing a phoneme, while an allograph is a concrete glyph variant used to render that grapheme. A glyph is the printed form; thus allographs are the glyphs that realize the same grapheme. This concept is distinct from allomorphy, which refers to alternate phonological or morphological forms of a morpheme.

Etymology: the term derives from Greek allos, meaning “other,” and graphē, meaning “writing.” The concept is widely used in linguistics, typography, and discussions of digital encoding.