Wiktionary
n. (context linguistics English) The study of the graphemes, or writing units, of a script, and of their relation to the phonemes of the spoken language
Wikipedia
Graphemics or graphematics is the linguistic study of writing systems and their basic components, i.e. graphemes.
At the beginning of the development of this area of linguistics, Ignace Gelb coined the term grammatology for this discipline; later some scholars suggested calling it graphology to match phonology, but that name is traditionally used for a pseudo-science. Others therefore suggested renaming the study of language-dependent pronunciation phonemics or phonematics instead, but this did not gain widespread acceptance either, so the terms graphemics and graphematics became more frequent.
Graphemics examines the specifics of written texts in a certain language and their correspondence to the spoken language. One major task is the descriptive analysis of implicit regularities in written words and texts (graphotactics) to formulate explicit rules ( orthography) for the writing system that can be used in prescriptive education or in computer linguistics, e.g. for speech synthesis.
In analogy to phoneme and ( allo) phone in phonology, the graphic units of language are graphemes, i.e. language-specific characters, and graphs, i.e. language-specific glyphs. Different schools of thought consider different entities to be graphemes; major points of divergence are the handling of punctuation, diacritic marks, digraphs or other multigraphs and non- alphabetic scripts.
Analoguous to phonetics, the " etic" counterpart of graphemics is called graphetics and deals with the material side only (including paleography, typography and graphology).