Coptic small letter khei

It brought Egyptian into a Greek-based alphabet.

Egyptian writing developed through hieroglyphs, cursive Hieratic and then Demotic. Demotic, a later Egyptian script, supplied seven signs for sounds Greek lacked.

Coptic also marked vowels in writing, unlike the earlier Egyptian scripts.

Why is ϧ linked to Bohairic?

Bohairic uses it; Sahidic does not.

Bohairic began in northern Egypt and spread after the Arab conquest of Egypt. By the 11th century it was virtually the only Coptic dialect used in Egypt; as of 2026 it remains the Coptic Church's liturgical language.