The division of speech into its parts, or of words into their categories, is the first preoccupation of every significant grammatical text in Arabic, starting with the opening lines of the Kitāb of Sībawayhi (d. ca. 180/796): hāḏā bābu ʿilmi mā l-kalimu min al-ʿarabiyya. fa-l-kalim: ismun, wa-fiʿlun, wa-ḥarfun jāʾa li-maʿnan laysa bi-smin wa-lā fiʿlin (I, 1 ed. Derenbourg/I, 2 ed. Būlāq). This can be translated fairly literally as ‘Chapter on the knowledge of what words are in Arabic. Those words are: name (ism), action (fiʿl), and a bit (ḥarf) which comes for some meaning and is n…