Among the earliest attempts to explain Pāṇini was the formulation of rules of interpretation or paribhāshās; a collection of these was made in the la… - Panini

The issue of theism vis-à-vis atheism, in the ordinary senses of the English words, played an important role in Indian thought. The ancient Indian tradition, however, classified the classical systems (darshanas) into orthodox (astika) and unorthodox (nastika). Astika does not mean “theistic,” nor does nastika mean “atheistic.” Panini, a 5th-century-BCE grammarian, stated that the former is one who believes in a transcendent world (asti paralokah) and the latter is one who does not believe in it (nasti paralokah).

The most successful, hence most prominent amongst these grammarians was Panini. His grammar, surpassing all others in tightness and precision, became the standard and remained so undisputedly until today. Panini was able to joint the original devanagari language into an exact framework of rules, thus preserving it for the posterity. Since his time, this language is called Sanskrit, “joined together, refined”.

Pāṇini had before him a list of irregularly formed words, which survives, in a somewhat modified form, as the Uṇādi Sūtra. There are also two appendixes to which Pāṇini refers: one is the Dhātupāṭha, "List of Verbal Roots," containing some 2000 roots, of which only about 800 have been found in Sanskrit literature, and from which about fifty Vedic verbs are omitted; the second is the Gaṇapāṭha, or "List of Word-Groups," to which certain rules apply. These gaṇas were metrically arranged in the Gaṇaratna-mahodadhi, composed by Vardhamāna in 1140 A.D.