Arabic is the language of the Qurʾān (or Koran, the sacred book of Islam) and the religious language of all Muslims. Literary Arabic, usually called Classical Arabic, is essentially the form of the language found in the Qurʾān, with some modifications necessary for its use in modern times; it is uniform throughout the Arab world. Colloquial Arabic includes numerous spoken dialects, some of which are mutually unintelligible. The chief dialect groups are those of Arabia, Iraq, Syria, Egypt, and North Africa. With the exception of the dialect of Algeria, all Arabic dialects have been strongly influenced by the literary language.