Sou and How Coptic Manuscripts Count

Numbers do a great deal of work in a Coptic manuscript. Quires are numbered so a binder can assemble them, folios and pages are numbered, chapters and scriptural divisions are numbered, dates are written out, and the Coptic calendar with its thirteen months requires figures constantly. All of this was done with letters rather than with a separate set of digits, in the alphabetic system Coptic took from Greek: the first nine letters count the units, the next nine the tens, the next nine the hundreds. That arrangement requires twenty seven signs, and the Greek alphabet in ordinary use has only twenty four, which is why sou and two further numeral only signs exist.

Coptic scribes distinguished a letter used as a figure by drawing a stroke above it, so a reader met no ambiguity even where a numeral stood in the middle of running text. The same convention marks the abbreviated sacred names Coptic inherited from Greek Christian book practice, and the two uses are told apart by context. The system has one further consequence that shaped how numbers were thought about across the Christian and Jewish east: because every letter carried a value, every written word carried a total. Greek writers called the practice of summing those totals isopsephy, and Hebrew tradition calls the equivalent gematria. Coptic possessed the same mechanism by inheritance, and the alphabet chart with sou in its sixth place is where the mechanism starts.