(plur. ʿAnāṣir) means, like aṣl, rukn, isṭuḳis (στοιχεĩον) etc., principle, basis, element in the general sense. It is used in the special sense of materia prima. The hellenising philosophers, as a rule, use arkān or isṭuḳisāt for the four elements of the sublunar world, which are composed of matter and form and, according to the prevailing view, are mutable. The material of the heavenly spheres is called rukn by these philosophers, more frequently however a fifth nature (ṭabʿ).
Sprenger, Dict. of Techn. Terms, p. 960 sqq.