Since the start of the Islamic conquest of the Maghreb in the 7th century ce, Berber and Arabic have been in continual contact. This has led to large-scale mutual influence. The sociolinguistic setting of this influence is not the same, though; Arabic influence on Berber is found in a situation of language maintenance with widespread bilingualism, while Berber influence on Arabic is no doubt to a large degree due to language shift by Berber speakers to Arabic. Linguistic influence is found on all levels: phonology, morphology, syntax, and lexicon. In those cases where only innovative patterns are shared between the two language groups, it is often difficult to make out where the innovation started; thus the great similarities in syllable structure between Maghrebian Arabic and northern Berber are the result of innovations within both language families, and it is difficult to tell where it started. Morphological influence seems to be mediated exclusively by lexical borrowing. Especially in Berber, this has led to parallel systems in the morphology, where native words always have native morphology, while loans either have nativized morphology or retain Arabic-like patterns. In the lexicon, it is especially Berber that takes over scores of loanwords from Arabic, amounting in one case to over one-third of the basic lexicon as defined by 100-word lists.
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.
As might be expected from the difficulty of traversing it, the Sahara Desert has been a fairly effective barrier to direct contact between its two edges; trans-Saharan language contact is limited to the borrowing of non-core vocabulary, minimal from south to north and mostly mediated by education from north to south. Its own inhabitants, however, are necessarily accustomed to travelling desert spaces, and contact between languages within the Sahara has often accordingly had a much greater impact. Several peripheral Arabic varieties of the Sahara retain morphology as well as vocabulary from the languages spoken by their speakers’ ancestors, in particular Berber in the southwest and Beja in the southeast; the same is true of at least one Saharan Hausa variety. The Berber languages of the northern Sahara have in turn been deeply affected by centuries of bilingualism in Arabic, borrowing core vocabulary and some aspects of morphology and syntax. The Northern Songhay languages of the central Sahara have been even more profoundly affected by a history of multilingualism and language shift involving Tuareg, Songhay, Arabic, and other Berber languages, much of which remains to be unraveled. These languages have borrowed so extensively that they retain barely a few hundred core words of Songhay vocabulary; those loans have not only introduced new morphology but in some cases replaced old morphology entirely. In the southeast, the spread of Arabic westward from the Nile Valley has created a spectrum of varieties with varying degrees of local influence; the Saharan ones remain almost entirely undescribed. Much work remains to be done throughout the region, not only on identifying and analyzing contact effects but even simply on describing the languages its inhabitants speak.