A siddha refers to a being who has achieved a high degree of physical as well as spiritual perfection or enlightenment. The ultimate demonstration of this is that siddhas allegedly attained physical immortality. Thus siddha, like siddhar refers to a person who has realized the goal of a type of sadhana and become a perfected being.

The siddhas had supremacies, which they divided into eight powers called attama-siddhi (8 siddhis). They contributed on Astrology, Medicines and Science for the welfare of human beings. Naadi and Jeeva Naadi is a very unique form of astrology formulated by them. This has been in existence for 1000s of years now.