Koppa (Greek letter)
Koppa or Qoppa (uppercase/lowercase ) was a letter of the Greek alphabet that was used in some Greek cities before the alphabet got its classic standard form. It is no longer used in normal writing today. It was pronounced as "k", just like Kappa (Κ). In the 5th century BC, people stopped using it and it fell out of use. Kappa then replaced it. In the order of the letters in the alphabet, it came between Pi and Rho, just like in the Latin alphabet the letter Q comes between P and R. However, they kept Koppa as a sign for the number "90" in the system of Greek numerals, but in a third numerical form. People still sometimes use it in this way, even though they do not use it as a letter to write words.