The word “tantra” is derived from the combination of two words “tattva” and “mantra”. “Tattva” means the science of cosmic principles, while “mantra” refers to the science of mystic sound and vibrations. Tantra therefore is the application of cosmic sciences with a view to attain spiritual ascendancy. In another sense, tantra also means the scripture by which the light of knowledge is spread: Tanyate vistaryate jnanam anemna iti tantram.
There are essentially two schools of Indian scriptures – “Agama” and “Nigama”. Agamas are those which are revelations while Nigama are the traditions. Tantra is an Agama and hence it is called “srutishakhavisesah”, which means it is a branch of the Vedas.