Khi: The Coptic Letter (Value 600), from Greek Chi

Khi is the twenty third letter of the Coptic alphabet and carries the numeral value six hundred. In Greek it wrote an aspirated k, and Coptic uses it in that role and also as a compression for the sequence kappa plus hori, following the same pattern as theta and phi. Egyptian had no aspirated k of its own that demanded a dedicated letter, so in independent use khi is chiefly at home in Greek loanwords and names. Its most conspicuous appearance in Coptic is not as a sound at all.

Coptic inherited from Greek Christian book practice the system of contracted sacred names, in which words such as God, Lord, Jesus, Christ and spirit are written as their first and last letters with a line drawn above, and the contraction for Christ begins with khi. That abbreviation is one of the most frequent things on any Christian manuscript page of the period, in Greek, Coptic, Latin, Syriac and Armenian alike, and it is one of the clearest pieces of evidence that early Christian book production was a single connected practice across languages. The letter also gave the monogram combining khi and rho that became a standard Christian sign in late antiquity, in Egypt as elsewhere. The monogram of khi and rho deserves a word of caution as well as of interest. It is a genuine and widespread late antique Christian sign, formed from the first two letters of the Greek word for Christ, and it appears in Egypt on the same range of objects as elsewhere in the Christian Mediterranean. What it is not is a Coptic invention, and its history belongs to the Greek Christian world Coptic was part of rather than to the Coptic script in particular.