Next we have the Vārttikas or "Notes" of Kātyāyana (probably third century B.C.) 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.

While Pāṇini's work is purely grammatical and lexicographic, cultural and geographical inferences can be drawn from the vocabulary he uses in examples, and from his references to fellow grammarians, which show he was a northwestern person. New deities referred to in his work include Vasudeva (4.3.98). The concept of dharma is attested in his example sentence dharmam carati "he observes the law" (cf. Taittiriya Upanishad 1.11).

The Mahābhāshya was commented on in the seventh century by Bhartṛihari in his Vākyapadīya which is concerned with the philosophy of grammar, and by Kaiyaṭa (probably thirteenth century). About 650 A.D. was composed the first complete commentary on Pāṇini, the Kāçikā Vṛitti or "Benares Commentary," by Jayāditya and Vāmana.

There is in the rules or definitions (sutras) of Panini a remarkably subtle and penetrating account of Sanskrit grammar. The construction of sentences, compound nouns, and the like is explained through ordered rules operating on underlying structures in a manner strikingly similar in part to modes of modern theory. As might be imagined, this perceptive Indian grammatical work held great fascination for 20th-century theoretical linguists. A study of Indian logic in relation to Paninian grammar alongside AristotleAristotelian]] and Western logic in relation to Greek grammar and its successors could bring illuminating insights.

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' (as is typical in Vedic learning). Writing first reappears in India in the form of the Brāhmī script from the 3rd century BC in the Ashokan inscriptions.

Pāṇini's grammar defines Classical Sanskrit, so Pāṇini by definition lived at the end of the Vedic period. He notes a few special rules, marked chandasi ("in the hymns") to account for forms in the Vedic scriptures that had fallen out of use in the spoken language of his time. These indicate that Vedic Sanskrit was already archaic, but still a comprehensible dialect.

While in the classical world scholars were dealing with language in a somewhat metaphysical way, the Indians were telling us what their language actually was, how it worked, and how it was put together. The methods and techniques for describing the structure of Sanskrit, which we find in Panini have not been substantially bettered to this day in modem linguistic theory and practice. We today employ many devices in describing languages that were already known to Panini's first two commentators.

In the fifteenth century Rāmachandra, in his Prakriyā-kaumudī, or "Moonlight of Method," endeavoured to make Pāṇini's grammar easier by a more practical arrangement of its matter. Bhaṭṭoji's Siddhānta-kaumudī (seventeenth century) has a similar aim; an abridgment of this work, the Laghu-kaumudī, by Varadarāja is commonly used as an introduction to the native system of grammar. Among non-Pāṇinean grammarians may be mentioned Chandra (about 600 A.D.), the pseudo-Çākaṭāyana (later than the Kāçikā), and, the most important, Hemachandra (12th century), author of a Prākrit grammar.

Panini’s grammar is the earliest scientific grammar in the world, the earliest extant grammar of any language, and one of the greatest ever written. It was the discovery of Sanskrit by the West, at the end of the 18th century, and the study of Indian methods of analyzing language that revolutionized our study of language and grammar, and gave rise to our science of comparative philology … The study of language in India was much more objective and scientific than in Greece or Rome. The interest was in empirical investigation of language, rather than philosophical and syntactical. Indian study of language was as objective as the dissection of a body by an anatomist.

A treatise called Astadhyayi (or Astaka) is Panini's major work. It consists of eight chapters, each subdivided into quarter chapters. In this work Panini distinguishes between the language of sacred texts and the usual language of communication. Panini gives formal production rules and definitions to describe Sanskrit grammar. Starting with about 1700 basic elements like nouns, verbs, vowels, consonants he put them into classes. The construction of sentences, compound nouns etc., is explained as ordered rules operating on underlying structures in a manner similar to modern theory. In many ways Panini's constructions are similar to the way that a mathematical function is defined today.

Panini was a Sanskrit grammarian who gave a comprehensive and scientific theory of phonetics, phonology, and morphology. Sanskrit was the classical literary language of the Indian Hindus and Panini is considered the founder of the language and literature. It is interesting to note that the word "Sanskrit" means "complete" or "perfect" and it was thought of as the divine language, or language of the gods.

Ashtadhyayi Sanskrit treatise on grammar was written in the 6th to 5th century BCE by the Indian grammarian Panini. This work set the linguistic standards for Classical Sanskrit. It sums up in 4,000 sutras the science of phonetics and grammar that had evolved in the Vedic religion. Panini divided his work into eight chapters, each of which is further divided into quarter chapters, beyond defining the morphology and syntax of Sanskrit language.

Panini's grammar is the earliest scientific grammar in the world, the earliest extant grammar of any language, and one of the greatest ever written. It was the discovery of Sanskrit by the West, at the end of the 18th century, and the study of Indian methods of analyzing language that revolutionized our study of language and grammar, and gave rise to our science of comparative philology... The study of language in India was much more objective and scientific than in Greece or Rome.

The descriptive Grammar of Sanskrit, which Panini, brought to its high- est perfection, is one of the greatest monuments of human intelligence and (what concerns us more) an indispensable model for description of languages. The only achievement in our field, which can take rank with it is the historical linguistics of the nineteenth century and this indeed owed its origin largely to Europe’s acquaintance with the Indian Grammar. One forgot that the Comparative Grammar of the Indo- European languages got its start only when the Paninian analysis of an Indo-European language became known in Europe. . . . If the accen- tuation of Sanskrit and Greek, for instance had been unknown, Verner could not have discovered the Pre-Germanic sound change, that goes by his name. Indo-European Comparative Grammar had (and has) at its service, only one complete description of a language, the grammar of Panini. For all other Indo-European languages it had only the traditional grammars of Greek and Latin woefully incomplete and unsystematic. (1933: 267–76)