Shai and Why Coptic Needed Letters Greek Could Not Supply

The Greek and Egyptian sound systems do not match, and the mismatch runs in both directions. Greek had aspirated stops, a cluster letter for k plus s and another for p plus s, and a distinction between long and short e and o. Egyptian had none of those as a matter of necessity, which is why gamma, delta and zeta live almost entirely in loanwords in Coptic and why ksi and psi are optional shorthands. Egyptian in turn had a set of consonants Greek simply lacked: sh, an f distinct from anything Greek wrote, a throat fricative, two affricates and a syllable of its own.

Seven letters were taken from Demotic to cover them, shai first among them. The decision to borrow from Demotic rather than to invent new shapes or to press Greek letters into double duty is the most consequential thing about the Coptic script. It kept the new writing connected to the old one, it produced an alphabet that could actually write the language, and it meant that the letters look Egyptian at exactly the points where the language is most Egyptian. A modern reader of a Coptic Orthodox service book meets shai and hori on the same line as alpha and omega, in a single continuous alphabet with nothing to mark where one tradition ends and the other begins.