"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."

“Next we have the Vārttikas or "Notes" of Kātyāyana on 1245 of Pāṇini's rules, and, somewhat later, numerous grammatical Kārikās or comments in metrical form: all this critical work was collected by Patanjali in his Mahābhāshya or "Great Commentary," with supplementary comments of his own. He deals with 1713 rules of Pāṇini.”

“The accepted cultivated speech of the contemporary language that Pāṇini describes in his Aṣṭādhyāyī must have coexisted with more vernacular varieties of speech in which there were features belonging to the Middle Indo-Aryan division of the language group. Several facts support this view.”

“It is not certain whether Pāṇini used writing for the composition of his work, though it is generally agreed that he knew of a form of writing, based on references to words such as "script" and "scribe" in his Ashtadhyayi. These must have referred to Aramaic or early Kharosthi writing. It is believed by some that a work of such complexity would have been difficult to compile without written notes, though others have argued that he might have composed it with the help of a group of students whose memories served him as 'notepads' . Writing first reappears in India in the form of the Brāhmī script from the 3rd century BC in the Ashokan inscriptions.”

“The Pāṇinian commentator Kātyāyana knew of the coexistence of Middle Indic forms with earlier ones. There is a Pāṇinian rule that provides that verb bases listed in an appendix to the Aṣṭādhyāyī have the class name dhātu . Kātyāyana discusses whether one could define verbal bases semantically and thereby possibly do without the verb list. He remarks that even if one defines a verbal base as denoting an action, the roots must be listed in order to preclude the possibility that constituents of terms such as āṇapayati/āṇavayati ‘commands’ be assigned the class name in question; āṇapayati/āṇavayati is a Middle Indic counterpart of Sanskrit ājñāpayati.”

“For example, the great linguist Panini gave the concept for meta-language-and constructed one-thousands of years before computer scientists began exploring the same idea. No one has been able to match him to this day.”

“Ashtadhyayi distinguishes between usage in the spoken language and usage that is proper to the language of the sacred texts. The Ashtadhyayi is generative as well as descriptive. With its complex use of metarules, transformations, and recursions, the grammar in Ashtadhyayi has been likened to the Turing machine, an idealized mathematical model that reduces the logical structure of any computing device to its essentials.”