The purpose of this study was to examine and analyse linguistic characteristics of the Middle Mongolian material named The Ras?lid Hexaglot, which is edited and published by Peter B. Golden in 2000. The Ras?lid Hexaglot is a six language vocabularia written by Al-Malik al-Afdal al-'Abb?s ibn 'Al?(1363-1377), a king of the Ras?lid dynasty in Yemen. It contains 6 languages: Arabic, Persian, Turkic, Greek, Armenian and Mongol language. The Mongolian language represented by the Arabic alphabet and demonstrates coincidences not only in the general Middle Mongolian characteristics but, going into details, shows distinctive elements in phonology and vocabulary.
After the exhaustive research the author ascertained following facts: I. It is well known that words of the group *V¹+γ/g+V¹ develops into any long vowel, but words of the group *V¹+γ/g+V² show a long vowel through the contraction. II. Vowels in initial syllable without emphasis used to be written with omission in Arabic transcription. III. Letters h? and w?w may represented any Mongolian long vowels. IV. Loan words aren't assimilated in Mongolian phonological system yet. V. Words of the Western Middle Mongolian are, in the aspect of the phonological developments, very similar to the Western Modern Mongolian, i.e. Khalmyk language.