Early Vedic texts (Rig Veda 1:164:45; 4:58:3; 10:125) suggest a structure for languages:
Language is composed of sentences with four stages of evolution that are expressed in three tenses (past, present and future). The sentences are composed of words that have two distinct forms of existence (vocal form, the word, and perceptional form, the meaning). These words are recognized mainly as verbs that represent real-world acts and nouns that take on seven cases depending on their mode of participation in real-world acts.
The number, seven, here is not very critical; the message is that the nouns are inflected into appropriate cases to indicate their mode of participation in concerned acts.
The Sanskrit grammarian Pāṇini (c. 520 – 460 BC) is the earliest known linguist and is often acknowledged as the founder of linguistics. He is most famous for formulating the 3,959 rules of Sanskrit morphology in the text Aṣṭādhyāyī, which is still in use today. Pāṇini’s grammar of Sanskrit is highly systematised and technical. Inherent in its analytic approach are the concepts of the phoneme, the morpheme and the root, only recognized by Western linguists some two millennia later.
His rules fully describe Sanskrit morphology without any redundancy. A consequence of his grammar’s focus on brevity is its highly unintuitive structure, reminiscent of contemporary “machine language” as opposed to “human readable” programming languages. His sophisticated logical rules and technique have been widely influential in ancient and modern linguistics.
Bhartrihari (c. 450 – 510) was another important author on Indic linguistic theory.
Bhartrihari theorized the act of speech as being made up of four stages: first, conceptualization of an idea, second, its verbalization and sequencing and third, delivery of speech into atmospheric air, all these by the speaker and last, the comprehension of speech by the listener, the interpreter.
The work of Pāṇini, and the later Indian linguist Bhartrihari, had a significant influence on many of the foundational ideas proposed by Ferdinand de Saussure, professor of Sanskrit, who is widely considered the father of modern structural linguistics.