Classical Arabic
State

The definite article spread areally among the Central Semitic languages and it would seem that Proto-Arabic lacked any overt marking of definiteness. Besides dialects with no definite article, the Safaitic inscriptions exhibit about four different article forms, ordered by frequency: h-, ʾ-, ʾl-, and hn-. The Old Arabic of the Nabataean inscriptions exhibits almost exclusively the form ʾl-. Unlike the Classical Arabic article, the Old Arabic ʾl almost never exhibits the assimilation of the coda to the coronals; the same situation is attested in the Graeco-Arabica, but in A1 the coda assimilates to the following d, αδαυρα * ʾad-dawra الدورة 'the region'.

In Classical Arabic, the definite article takes the form al-, with the coda of the article exhibiting assimilation to the following dental and denti-alveolar consonants. Note the inclusion of palatal /ɕ/, which alone among the palatal consonants exhibits assimilation, indicating that assimilation ceased to be productive before that consonant shifted from Old Arabic /ɬ/:
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