This paper attempts to reconstruct aspects of the phonology and morphology of the Arabic of the Islamic conquests on the basis of Greek transcriptions in papyri of the first Islamic century. The discussion includes phonemic and allophonic variation in consonants and vowels, and nominal morphology. The essay concludes with a discussion on possible Aramaic and South Arabian influences in the material, followed by a short appendix with remarks on select Arabic terms from the pre-Islamic papyri.