Nirukta/Nirvacana is the native tradition of semantic derivation or etymology. It is traditionally regarded as one of the six ancillary Vedic disciplines (vedāṅga). The most important work in the Nirukta/Nirvacana tradition is Yāska’s Nirukta (possibly c. 550 BC), essentially a commentary on the Nighaṇṭu, a list of words mainly extracted from the Ṛgveda. The essential feature of the Nirukta is the semantic interpretation of words based on their derivation. For example, the Nirukta teaches that nouns are derived from verbs (Nirukta 1.12 nāmāni ākhyātajāni), such that a semantic derivation is essentially an elucidation of the link between the meaning of the noun and the underlying action of the verb. For instance, the noun ap-/āp- ‘water’ is associated with the verbal root √āp ‘to reach’ and is explained as ‘that which reaches something’.