Koppa or Qoppa (uppercase/lowercase Ϙ ϙ) 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 only wrote Kappa. 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. People still sometimes use it in this way, even though they do not use it as a letter to write words.
The letter Koppa at first looked like a circle with a small bar under it. Later it was written more like a pointed S.