The word ‘Upanishad’ denotes Brahma-vidya by its derivation. Sri Sankara Bhagavatpada says in his Bhashya on the Kathopanishad that this word is derived by adding the prefixes ‘upa’ (meaning near) and ‘ni’ (with certainty) to the root ‘sad’ which means ‘to destroy’, ‘to reach’, and ‘to loosen’. Thus the meaning of the word ‘Upanishad’ is that it is the knowledge that destroys the seeds of worldly existence such as ignorance in the case of those seekers of liberation who, after becoming free from all desires approach (upa sad) this knowledge.