Demotic is both a stage of the Egyptian language and, more precisely, the highly cursive script devised for it around the seventh century BCE out of the earlier hieratic. It was made for speed and for volume, and its first use was administrative: contracts, receipts, letters, tax records and court documents, in a hand so abbreviated that individual signs are frequently unrecognisable outside their usual groupings.
Mark Depauw's companion to the field sets out the scale of what survives and the difficulty of reading it, which is why Demotic studies remained a specialism long after hieroglyphic Egyptian had been opened up. The Rosetta Stone carries Demotic as its middle register, between hieroglyphs and Greek, and it was the Demotic text that was deciphered first.
What began as a bureaucratic hand became literary and then religious. Demotic carries narrative cycles about the magician Setne Khaemwaset and about Inaros, wisdom instructions, and a substantial body of ritual and magical material. The Greek Magical Papyri, edited by Hans Dieter Betz, include spells in which Demotic and Greek alternate within a single text and sometimes within a single procedure, which is direct evidence of how the two traditions were used together by the same practitioners.