The Romans added V at once, which was sorely needed, then X for 'ks,' pronounced like the Greek X All the letters beyond T are later additions to the alphabet. The Phoenician alphabet only went up to T. Koppa became the model for Q, which in Latin was always used in the combination QV, pronounced 'kw,' a sound that does not occur in Greek. Gaius was also spelled Caius, and its abbreviation was always C. Eventually, K became vestigial in Latin, used only for a few words like Kalendae and Kaeso (a name). Z was a sound not used in Latin, so it was thrown out of the alphabet and replaced by a modified C, a C with a tail, for the 'g' sound. Latin also used the K for the 'k' sound at that time, but the C spelling became popular. The gamma was written C in Etruscan, and represented both the hard 'g' and 'k' sounds in Latin, which was confusing. The digamma, which represented a 'w' sound in Greek was adopted for the different Latin sound 'f' that did not occur in Greek. Green letters are those introduced later, after the alphabets had been adopted, and red letters are those that were eliminated from the archaic alphabet. A comparison of the Greek and Latin alphabets shows the close relation between the two. The letters J, U, and W of the modern alphabet were added in medieval times, and did not appear in the classical alphabet, except that J and U could be alternative forms for I and V. The Latin alphabet of 23 letters was derived in the 600's BC from the Etruscan alphabet of 26 letters, which was in turn derived from the archaic Greek alphabet, which came from the Phoenician.