Definition: name of a class of works which were composed to explain the collections of Vedic words by means of proposing derivations of those words from roots as would suit the sense. The Nirukta works are looked upon as supplementary to grammar works and there must have been a good many works of this kind in ancient times as shown by references to the writers of these viz. Upamanyu, Sakatayana,Sakapuni,Sakapurti and others, but, out of them only one work composed by Yaska has survived; the word, hence has been applied by scholars to the Nirukta of Yaska which is believed to have been written in the seventh or the eighth century B. C. i. e. a century or two before Panini. The Nirukta works were looked upon as subsidiary to the study of the Vedas along with works on phonetics (शिक्षा), rituals (कल्प), grammar (व्याकरण) prosody (छन्दस्) and astronomy(ज्योतिष)and a mention of them is found made in the Chandogyopanisad. As many of the derivations in the Nirukta appear to be forced and fanciful, it is doubtful whether the Nirukta works could be called scientific treatises. The work of Yaska, however, has got its own importance and place among works subsidiary to the Veda, being a very old work of that kind and quoted by later commentators. There were some glosses and commentary works written upon Yaska's Nirukta out of which the one by Durgacarya is a scholarly one.It is doubtful whether Durgacarya is the same as Durgasimha, who wrote a Vrtti or gloss on the Katantra Vyakarana. The word निरुक्त is found in the Pratisakhya works in the sense of 'explained' and not in the sense of derived; cf. R. Pr. XV 6; V.Pr. IV. 19, 195.