Theta: The Coptic Letter (Value 9), from Greek Theta

Theta is the ninth letter of the Coptic alphabet and carries the numeral value nine, closing the run of units before the tens begin at iota. In Greek it wrote an aspirated t, a t followed by a puff of breath, and Coptic took it over in that role. What Coptic then did with it is more interesting than the borrowing itself. Egyptian has a letter of its own for the h sound, hori, one of the seven signs brought in from Demotic because no Greek letter covered them, and Coptic treats theta as a compact equivalent of the sequence t plus hori.

The consequence is that a great many Coptic words have two legitimate spellings, one using theta and one writing out the two letters, and manuscripts differ over which they prefer. That variation is not carelessness. It follows dialect and scribal tradition closely enough that an editor can use it as evidence when placing an undated manuscript, alongside the vowel correspondences that separate Sahidic from Bohairic and from the smaller regional forms. Theta is thus a place where the borrowed Greek series and the Egyptian additions to it meet and overlap rather than simply sitting side by side. The same is true of ksi and psi, both of which write clusters that Coptic can also spell out letter by letter. Coptic did not just take the Greek alphabet; it kept renegotiating what to do with the parts of it that did not fit an Egyptian mouth.