Yāska was an ancient Indian grammarian and linguist [est. 7th–5th century BCE(disputed)]. Preceding Pāṇini [est. 7th–4th century BCE(disputed)], he is traditionally identified as the author of Nirukta, the discipline of "etymology" (explanation of words) within Sanskrit grammatical tradition and the Nighantu, the oldest proto-thesaurus in India. Yaska is widely regarded as the precursive founder of the discipline of what would become etymology in both the East and the West. "यास्काचार्यो यस्कस्य अपत्यं स्यात्" The name Yaaska is probably a patronymic name meaning of Yaska यस्क. It is uncertain however who Yaska यस्क could have been."अपि पाणिनीयदृश्यते" The patronymic of Yaska is also seen in Panini's great work: The Astadhyayi (See Kashika commentary on Sutra फक्फिञोरन्यतरस्याम्). The list of Brihadaranyaka Upanishad, regarding, vamshas, says that Yaska could be a teacher of Bharadwaj भरद्वाज or a contemporary of him.
Pāṇini cites at least ten grammarians and linguists before him. According to Sumitra Mangesh Katre, the ten Vedic scholar names he quotes are of Apisali, Kashyapa, Gargya, Galava, Cakravarmana, Bharadvaja, Sakatayana, Sakalya, Senaka and Sphotayana.
Determining the exact century of Yaska is difficult, and opinions of different scholars vary from 7th–5th century BC. Pāṇini mentions Yaska as one of the previous linguists, and so Yaska must precede Pāṇini.
Yaska is the author of the Nirukta, a technical treatise on etymology, and the semantics of Sanskrit words. He is thought to have succeeded , an old grammarian and expositor of the Vedas, who is mentioned in his text.
The Nirukta attempts to explain how certain words get to have their meanings, especially in the context of interpreting the Vedic texts. It includes a system of rules for forming words from roots and affixes, and a glossary of irregular words, and formed the basis for later lexicons and dictionaries. It consists of three parts, viz.: (i) Naighantuka, a collection of synonyms; (ii) Naigama, a collection of words peculiar to the Vedas, and (iii) Daivata, words relating to deities and sacrifices.