Ro: The Coptic Letter (Value 100), from Greek Rho

Ro is the eighteenth letter of the Coptic alphabet and the first of the hundreds in the numeral series, standing for one hundred. It writes the r sound and is common in both the Egyptian and the Greek layers of Coptic vocabulary. Its interest lies in what it makes visible. For three thousand years Egyptian was written in scripts that used the same signs for r and for l, with no way of marking which sound a given word contained, so that a fundamental consonantal distinction was simply absent from the page. Egyptologists compensate with transliteration conventions and with evidence from the way Egyptian names were spelled in other languages, all of it indirect.

Coptic ends the difficulty at a stroke, because the Greek alphabet supplied a rho and a lambda as separate letters and Coptic took both. From that moment the words separate, and because Coptic is a late stage of the same language, the Coptic form of a word became a standard witness for reconstructing the consonants of its ancient ancestor. That evidence has limits. Two thousand years of sound change separate Coptic from Middle Egyptian, the dialects disagree with each other, and a Coptic form is a descendant rather than a photograph. But it is direct evidence of a kind the earlier scripts do not supply at all, and letters like ro are the reason it exists.