I have been reading a few websites lately which mention three Greek letters that disappeared completely by classical Greek; Digamma, Koppa, and Stigma. Were there more letters that went out of use by the classical era? I have one source which says that there were more letters which are no longer in use today. I am curious about this. Also, I'd like to know what they looked like, particularly the Stigma, and what order they came in the alphabet.<br /><br />Thanks!