Cherology
Cherology and chereme (from Ancient Greek: χείρ "hand") are synonyms of phonology and phoneme previously used in the study of sign languages.
A chereme, as the basic unit of signed communication, is functionally and psychologically equivalent to the phonemes of oral languages, and has been replaced by that term in the academic literature. Cherology, as the study of cheremes in language, is thus equivalent to phonology.