Hejazi Arabic
Hejazi Arabic or Hijazi Arabic ( '), also known as West Arabian Arabic, is a variety of Arabic spoken in the Hejaz region in Saudi Arabia. Strictly speaking, there are two main groups of dialects spoken in the Hejaz region, one by the urban population, originally spoken in the major cities of Jeddah, Mecca and Medina, and another by the Bedouin or rural populations. However, the term most often applies to the urban variety which is discussed in this article.
Arabic
Even during Muhammad's lifetime, there were dialects of spoken Arabic. Muhammad spoke in the dialect of Mecca, in the western Arabian peninsula, and it was in this dialect that the Quran was written down. However, the dialects of the eastern Arabian peninsula were considered the most prestigious at the time, so the language of the Quran was ultimately converted to follow the eastern phonology. It is this phonology that underlies the modern pronunciation of Classical Arabic. The phonological differences between these two dialects account for some of the complexities of Arabic writing, most notably the writing of the glottal stop or "hamzah" (which was preserved in the eastern dialects but lost in western speech) and the use of ' (representing a sound preserved in the western dialects but merged with ' in eastern speech).