Afroasiatic languages are the fourth largest linguistic phylum, spoken by some 350 million people in North, West, Central, and East Africa, in the Middle East, and in scattered communities in Europe, the United States, and the Caucasus. Some Afroasiatic languages, such as Arabic, Hausa, Amharic, Somali, and Oromo, are spoken by millions of people, while others are endangered with extinction. As of the early 21st century, the phylum is composed of six families: Egyptian (extinct), Semitic, Cushitic, Omotic, Berber, and Chadic. There are some typological features shared by all families, particularly in the domain of phonology. Languages are also typologically quite distinct with respect to syntax and functions encoded in the grammatical systems. Some Afroasiatic languages, such as Egyptian, Akkadian, Phoenician, Hebrew, Arabic, and Ge’ez, have a longtime written tradition, but for many languages no writing system has yet been proposed or adopted. The Old Semitic writing system gave rise to the modern alphabets used in thousands of unrelated contemporary languages. Two Semitic languages, Hebrew (with some Aramaic) and Arabic, were used to write the Old Testament and the Koran, the holy books of Judaism and Islam.