Middle Armenian

Middle Armenian, also called Cilician Armenian, corresponds to the second period of Armenian which was spoken and written in between the 12th and 18th centuries. It comes after Grabar and before Ashkharhabar.
Classical Armenian was predominantly an inflecting and synthetic language, but in Middle Armenian, during the period of Modern Armenian influence, agglutinative and analytical forms influenced the language. In this respect, Middle Armenian is a transition stage from Old Armenian to Modern Armenian. Middle Armenian is notable for being the first written form of Armenian to display Western-type voicing qualities and to have introduced the letters օ and ֆ, which were based on the Greek letters "o" and "φ".

Additions

The letter օ, based on the Greek letter o, was added during this period. It originally represented the IPA sound , which developed out of the Classical Armenian diphthong աւ. Today, in the Armenian alphabet, it represents IPA and is indistinguishable in most cases from ո. Therefore, in standard orthography, o is only written word-initially.
The letter ֆ, based on the Greek letter φ, was added during this period. It represents the IPA sound , which is not a native phoneme in Armenian. However, it was prevalent in borrowed words, making it necessary to use a letter to write it. It is still used today in the Armenian alphabet.