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). Standardization Abu al-Aswad al-Du'ali (–689) is credited with standardizing Arabic grammar, or an-naḥw ( "the way"), and pioneering a system of diacritics to differentiate consonants ( nuqat l-i'jām "pointing for non-Arabs") and indicate vocalization ( at-tashkil). Al-Khalil ibn Ahmad al-Farahidi (718 – 786) compiled the first Arabic dictionary, Kitāb al-'Ayn ( "The Book of the Letter ع"), and is credited with establishing the rules of Arabic prosody. Al-Jahiz (776-868) proposed to Al-Akhfash al-Akbar an overhaul of the grammar of Arabic, but it would not come to pass for two centuries. The standardization of 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. Spread Arabic spread with the spread of Islam. Following the early Muslim conquests, Arabic gained vocabulary from Middle Persian and Turkish. In the early Abbasid period, many Classical Greek terms entered Arabic through translations carried out at Baghdad's House of Wisdom. By the 8th century, knowledge of Classical Arabic had become an essential prerequisite for rising into the higher classes throughout the Islamic world, both for Muslims and non-Muslims. For example, Maimonides, the Andalusi Jewish philosopher, authored works in Judeo-Arabic—Arabic written in Hebrew script—including his famous The Guide for the Perplexed (, Dalālat al-ḥāʾirīn). Development Ibn Jinni of Mosul, a pioneer in phonology, wrote prolifically in the 10th century on Arabic morphology and phonology in works such as Kitāb Al-Munṣif, Kitāb Al-Muḥtasab, and . Ibn Mada' of Cordoba (1116–1196) realized the overhaul of Arabic grammar first proposed by Al-Jahiz 200 years prior. The Maghrebi lexicographer Ibn Manzur compiled Lisān al-ʿArab (, "Tongue of Arabs"), a major reference dictionary of Arabic, in 1290. Neo-Arabic Charles Ferguson's koine theory 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