Ashtadhyayi
The Ashtadhyayi (IAST: Aṣṭādhyāyī Devanagari: अष्टाध्यायी) is the central part of Pāṇini's grammar, and by far the most complex. Its extreme compactness without sacrificing completeness would become the model for later technical texts or sūtras which specialize in compatness and completeness at the expense of clarity. It takes material from the lexical lists (Dhatupatha, Ganapatha) as input and describes algorithms to be applied to them for the generation of well-formed words. It is highly systematised and technical. Inherent in its approach are the concepts of the phoneme, the morpheme and the root. His rules have a reputation for perfection — that is, they are claimed to describe Sanskrit morphology fully, without any redundancy. A consequence of his grammar's focus on brevity is its highly unintuitive structure, reminiscent of modern notations such as the "Backus–Naur Form". His sophisticated logical rules and technique have been widely influential in ancient and modern linguistics.
The Ashtadhyayi was not the first description of Sanskrit grammar, but it surpassed its predecessor on such a monumental scale that all earlier works are now lost except for the extent to which they are mentioned by Panini. The Ashtadhyayi became the foundation of Vyākaraṇa (Sanskrit grammatical tradition), and the classical works of Sanskrit grammarians which flourished during ca. the 8th and 15th centuries (and a revival in the 17th and 18th) are essentially commentaries on Panini.
In the Ashtadhyayi, language is observed in a manner that has no parallel among Greek or Latin grammarians. Pāṇini's grammar marks the entry of the non-sacred into Indian thought, and according to Renou and Filliozat, it then defines the linguistic expression of that thought. Pāṇini made use of a technical metalanguage consisting of a syntax, morphology and lexicon. This metalanguage is organised according to a series of meta-rules, some of which are explicitly stated while others can be deduced. The two fundamental principles on which the metalanguage is based are non-redundancy, or the principle of economy, and the necessity of all the rules in the Ashtadhyayi.
The Ashtadhyayi consists of 3,959 sutras (sūtrāṇi) or rules, distributed among eight chapters, which are each subdivided into four sections or padas (pādāḥ).
From example words in the text, and from a few rules depending on the context of the discourse, additional information as to the geographical, cultural and historical context of Pāṇini can be discerned.
Read more about this topic: Panini (grammarian)