As per Hindu philosophy, Aja is one that has no origin. Aja stands for jiva, Brahma, Vishnu, Shiva, Chandra, Kamadeva, the Supreme Being, etc. The Supreme Being is unborn and unmanifest because He is the creator of everything. Everything originates from Him. Aja implies that which has no limit, without beginning and without end. It also means nitya (given). This is the true nature of Brahman. The jiva, on the other hand, is born and has certain limitations. Jiva is bound by maya (the principle/instrument/power of differential construction) and attains liberation by the removal of bondage of maya (a construct).
In the Samkhya system of philosophy prakriti is called unborn, i.e, aja. From prakriti originates everything. Prakriti is the first ause of the universe. It accounts for whatever is physical, both matter and force. It is constituted of the three gunas (qualities) – sattva, rajas and tamas. Svetasvatara Upanishad (IV.5), describes aja as that which has red, white and black colors and gives birth to many like herself.