In Classical Sanskrit, the noun acquires the neuter gender and may express the concept of "aether" (Manusmriti, Shatapatha Brahmana).
In Vedantic philosophy, the word acquires its technical meaning of "an ethereal fluid imagined as pervading the cosmos".
The first category, represented by the Nyaya, Vaisheshika, Purva Mimamsa, and Jain traditions, considers Akasha to be an independent, all-pervading, and eternal substance essential to the structure of the universe.
[2] In Hinduism, akasha means the basis and essence of all things in the material world; the first element created.
The Nyaya and Vaisheshika schools of Hindu philosophy state that akasha (aether) is the fifth physical substance, which is the substratum of the quality of sound.
[5] In the Linga Purana (Volume I, Chapter 65), akasha is translated as "aether" and listed as one of the 1000 names of Shiva.
[12] Philosophically, ākāśa is considered one of the uncompounded phenomena (asaṃskṛtadharmas) in six Buddhist schools, including the Sarvāstivāda, Mahāsāṃghika, and later Yogācāra.