Why is Coptic important for the history of the Egyptian language?

Coptic is of paramount importance to the history of the Egyptian language because it represents the final stage of the language's development. Its significance is primarily twofold:12

• Linguistic Continuity: As the last stage of ancient Egyptian, Coptic provides a direct link to the language's evolution from its earlier forms. Unlike previous stages that utilized hieroglyphic, hieratic, or demotic scripts—which did not record vowels—Coptic was written using the Greek alphabet supplemented by seven characters from demotic script. This alphabetic system makes Coptic directly readable, offering scholars essential insights into the phonetic structure of the language that are otherwise obscured in earlier, non-vocalized scripts.1324

• Decipherment: Coptic was instrumental in the successful decipherment of ancient Egyptian hieroglyphs. By comparing the three known Egyptian scripts with the well-understood Coptic language, Jean-François Champollion was able to recognize that hieroglyphic writing was a phonetic system rather than merely symbolic, ultimately unlocking the ability to read and translate ancient Egyptian texts.4