Siddhi in the context of Ṛddhi

Siddha (Sanskrit: सिद्ध siddha; "perfected one") is a term that is used widely in Indian religions and culture. It means "one who is accomplished." It refers to perfected masters who have achieved a high degree of perfection of the intellect as well as liberation or enlightenment. In Jainism, the term is used to refer to the liberated souls. Siddha may also refer to one who has attained a siddhi, paranormal capabilities.

Siddhas may broadly refer to siddhars, naths, ascetics, sadhus, or yogis because they all practice sādhanā.

The Siddhar (Tamil (romanized) cittar; from Sanskrit siddha) in Tamil tradition is a perfected individual who has attained spiritual powers called siddhi.

Historically, Siddhar also refers to the people who were early-age wandering adepts that dominated ancient Tamil teaching and philosophy. They were knowledgeable in science, technology, astronomy, literature, fine arts, music, drama, and dance and provided solutions to common people's illnesses and advice for their future. Some of their ideologies are considered to have originated during the First Sangam period.

Mahasiddha (Sanskrit: mahāsiddha "great adept; Tibetan: གྲུབ་ཐོབ་ཆེན་པོ, Wylie: grub thob chen po, THL: druptop chenpo) is a term for someone who embodies and cultivates the "siddhi of perfection". A siddha is an individual who, through the practice of sādhanā, attains the realization of siddhis, psychic and spiritual abilities and powers.

Mahasiddhas were practitioners of yoga and tantra, or tantrikas. Their historical influence throughout the Indian subcontinent and the Himalayas was vast and they reached mythic proportions as codified in their songs of realization and hagiographies, or namtars, many of which have been preserved in the Tibetan Buddhist canon. The Mahasiddhas are identified as founders of Vajrayana traditions and lineages such as Dzogchen and Mahamudra, as well as among Bön, Nāth, and Tamil siddhars, with the same Mahasiddha sometimes serving simultaneously as a founding figure for different traditions.