Zij (astronomical handbook with tables)

Zij is the Arabic name for a class of astronomical books that set out higher spherical astronomy and the methods of computing celestial motions, contain all the tables required, and usually leave aside the rudiments of cosmography. ¹

Nallino says Europeans wrongly translated zij as "Tables" (Tabulae), whereas the Arabs always call a table a jadwal, from the likeness of its columns to jadawil, little water channels. ¹ He holds that al-Battani called his own book simply a zij, and that early authors knew his Zij by that name. ¹

Nallino contrasts the zij with the Almagest: the Almagest tries to embrace all of ancient astronomy so the student needs no other book, with long demonstrations mixed with numerical examples, whereas a zij is written not for beginners but for practitioners of computation. ² Zijes also customarily treat problems of spherical astronomy that astrological computation requires and that Ptolemy and Theon omit — fixing the houses, the revolutions of years, the projection of rays; Nallino thinks the Arabs thereby fostered a celestial mathematics that had been slight among Greek astrologers. ³