stylistic:tone, information:classification
Ancient and medieval era

The 5th-century BCE scholar Pāṇini in his Sutra 1.4.54–55 of Sanskrit grammar, cryptically explains tantra through the example of "Sva-tantra" (Sanskrit: स्वतन्त्र), which he states means "independent" or a person who is his own "warp, cloth, weaver, promoter, karta (actor)". Patanjali in his Mahābhāṣya quotes and accepts Panini's definition, then discusses or mentions it at a greater length, in 18 instances, stating that its metaphorical definition of "warp (weaving), extended cloth" is relevant to many contexts. The word tantra, states Patanjali, means "principal, main".

He uses the same example of svatantra as a composite word of "sva" (self) and tantra, then stating "svatantra" means "one who is self-dependent, one who is his own master, the principal thing for whom is himself", thereby interpreting the definition of tantra. Patanjali also offers a semantic definition of Tantra, stating that it is structural rules, standard procedures, centralized guide or knowledge in any field that applies to many elements.

Starting in the early centuries of the common era, newly revealed Tantras centering on Vishnu, Shiva or Shakti emerged. There are tantric lineages in all main forms of modern Hinduism, such as the Shaiva Siddhanta tradition, the Shakta sect of Shri Vidya, the Kaula, and Kashmir Shaivism.

The ancient Mimamsa school of Hinduism uses the term tantra extensively, and its scholars offer various definitions. For example:

When an action or a thing, once complete, becomes beneficial in several matters to one person, or to many people, that is known as Tantra. For example, a lamp placed amidst many priests. In contrast, that which benefits by its repetition is called Āvāpa, such as massaging with oil. (...)

Medieval texts present their own definitions of Tantra. Kāmikā-tantra, for example, gives the following explanation of the term tantra:

Because it elaborates (tan) copious and profound matters, especially relating to the principles of reality (tattva) and sacred mantras, and because it provides liberation (tra), it is called a tantra.