The Relationship Between Hieroglyphic, Hieratic and Demotic
Prior to the creation of the Coptic alphabet in 300 AD, the Egyptian language was written in three non-alphabetic scripts; Hieroglyphic, Hieratic and Demotic. Each of these used a combination of pictographic/ideographic symbols and phonetic symbols, but it is important to recognize that they were three distinct scripts.
Hieroglyphic and Hieratic writing developed concurrently and independently of one another. They were closely related, though the exact nature of their relationship is unknown. There is little evidence to suggest that one descended from the other, but it is probable that they were mutually influential. Hieratic was the more cursive of the two. Both scripts were used from roughly 3200 BC until 400 AD. Generally, Hieroglyphics were used for monumental inscriptions and decorative texts, and Hieratic was used for administrative texts which placed more importance in content than appearance, which were written by hand, and which needed to be written quickly.
Demotic writing developed around 600 BC. It was derived from Hieratic writing, but developed into a highly cursive form so that the pictographic element of some symbols was lost. Although many single symbols were still used to write whole words or concepts, the symbol did not necessarily visually resemble the concept it represented. As Demotic writing gained popularity, it began to replace Hieratic writing in the administrative context, though Hieratic continued to be used in religious texts. Demotic writing was used until roughly 400 AD, when all three scripts began to fall from use in favour of the Coptic alphabet.
Note that there is significant overlap in the dates during which the three scripts were used. None of them entirely replaced another; they all were used concurrently in restricted domains.
Reference: Jacques Kinnaer, Writing in Ancient Egypt (WayBackMachine)
This article formerly appeared on ScriptSource.