Arabic is a Central Semitic language, closely related to the Northwest Semitic languages (Aramaic, Hebrew, Ugaritic, and Phoenician), the Ancient South Arabian languages, and various other Semitic languages of Arabia such as Dadanitic. The Semitic languages changed a great deal between Proto-Semitic and the establishment of the Central Semitic languages, particularly in grammar. Innovations of the Central Semitic languages—all maintained in Arabic—include:
- The conversion of the suffix-conjugated stative formation (jalas-) into a past tense.
- The conversion of the prefix-conjugated preterite-tense formation (yajlis-) into a present tense.
- The elimination of other prefix-conjugated mood/aspect forms (e.g., a present tense formed by doubling the middle root, a perfect formed by infixing a /t/ after the first root consonant, probably a jussive formed by a stress shift) in favor of new moods formed by endings attached to the prefix-conjugation forms (e.g., -u for indicative, -a for subjunctive, no ending for jussive, -an or -anna for energetic).
- The development of an internal passive.
There are several features which Classical Arabic, the modern Arabic varieties, as well as the Safaitic and Hismaic inscriptions share which are unattested in any other Central Semitic language variety, including the Dadanitic and Taymanitic languages of the northern Hejaz. These features are evidence of common descent from a hypothetical ancestor, Proto-Arabic. The following features can be reconstructed with confidence for Proto-Arabic:
- negative particles m *mā; lʾn *lā-ʾan > CAr lan
- mafʿūl G-passive participle
- prepositions and adverbs f, ʿn, ʿnd, ḥt, ʿkdy
- a subjunctive in -a
- leveling of the -at allomorph of the feminine ending
- ʾn complementizer and subordinator
- the use of f- to introduce modal clauses
- independent object pronoun in (ʾ)y
- vestiges of nunation
Arabia boasted a wide variety of Semitic languages in antiquity. In the southwest, various Central Semitic languages both belonging to and outside of the Ancient South Arabian family (e.g. Southern Thamudic) were spoken. It is also believed that the ancestors of the Modern South Arabian languages (non-Central Semitic languages) were also spoken in southern Arabia at this time. To the north, in the oases of northern Hejaz, Dadanitic and Taymanitic held some prestige as inscriptional languages. In Najd and parts of western Arabia, a language known to scholars as Thamudic C is attested. In eastern Arabia, inscriptions in a script derived from ASA attest to a language known as Hasaitic. Finally, on the northwestern frontier of Arabia, various languages known to scholars as Thamudic B, Thamudic D, Safaitic, and Hismaic are attested. The last two share important isoglosses with later forms of Arabic, leading scholars to theorize that Safaitic and Hismaic are in fact early forms of Arabic and that they should be considered Old Arabic.
Beginning in the 1st century CE, fragments of Northern Old Arabic are attested in the Nabataean script across northern Arabia. By the 4th century CE, the Nabataean Aramaic writing system had come to express varieties of Arabic other than that of the Nabataeans.
Old Hejazi and Classical Arabic
In late pre-Islamic times, a transdialectal and transcommunal variety of Arabic emerged in the Hejaz which continued living its parallel life after literary Arabic had been institutionally standardized in the 2nd and 3rd century of the Hijra, most strongly in Judeo-Christian texts, keeping alive ancient features eliminated from the "learned" tradition (Classical Arabic). This variety and both its classicizing and "lay" iterations have been termed Middle Arabic in the past, but they are thought to continue an Old Higazi register. It is clear that the orthography of the Qur'an was not developed for the standardized form of Classical Arabic; rather, it shows the attempt on the part of writers to record an archaic form of Old Higazi.
In the late 6th century AD, a relatively uniform intertribal "poetic koine" distinct from the spoken vernaculars developed based on the Bedouin dialects of Najd, probably in connection with the court of al-Ḥīra. During the first Islamic century, the majority of Arabic poets and Arabic-writing persons spoke Arabic as their mother tongue. Their texts, although mainly preserved in far later manuscripts, contain traces of non-standardized Classical Arabic elements in morphology and syntax. The standardization of Classical Arabic reached completion around the end of the 8th century. The first comprehensive description of the ʿarabiyya "Arabic", Sībawayhi's al-Kitāb, is based first of all upon a corpus of poetic texts, in addition to Qur'an usage and Bedouin informants whom he considered to be reliable speakers of the ʿarabiyya. By the 8th century, knowledge of Classical Arabic had become an essential prerequisite for rising into the higher classes throughout the Islamic world.
Charles Ferguson's koine theory (Ferguson 1959) claims that the modern Arabic dialects collectively descend from a single military koine that sprang up during the Islamic conquests; this view has been challenged in recent times. Ahmad al-Jallad proposes that there were at least two considerably distinct types of Arabic on the eve of the conquests: Northern and Central (Al-Jallad 2009). The modern dialects emerged from a new contact situation produced following the conquests. Instead of the emergence of a single or multiple koines, the dialects contain several sedimentary layers of borrowed and areal features, which they absorbed at different points in their linguistic histories.
According to Veersteegh and Bickerton, colloquial Arabic dialects arose from pidginized Arabic formed from contact between Arabs and conquered peoples. Pidginization and subsequent creolization among Arabs and arabized peoples could explain relative morphological and phonological simplicity of vernacular Arabic compared to Classical and MSA.