Khi

It is known, from the existence in his time¹ of the Delphic tripod, that all these letters existed in 480 B.C. ; but on that monument the Khi and Psi differ from the forms used later.

The letters upsilon, phi, khi, psi, δ were Greek additions

Greek scripts display notable local characteristics — principally with regard to the shape of letters but also in the matter of the phonetic values attributed to signs such as san, sigma, khi, and psi.