The writing systems used in ancient Egypt were deciphered in the early nineteenth century through the work of several European scholars, especially Jean-François Champollion and Thomas Young. Ancient Egyptian forms of writing, which included the hieroglyphic, hieratic and demotic scripts, ceased to be understood in the fourth and fifth centuries AD, as the Coptic alphabet was increasingly used in their place. Later generations' knowledge of the older scripts was based on the work of Greek and Roman authors whose understanding was faulty.