Ayurveda is Shashvata which means eternal, and Anadi means without a beginning in existence since time immemorial.

Brahma recollected Ayurveda and compiled it in treatise form Brahma Samhita ' even before creating the world. This Brahma Samhita is comprised of one lakh slokas which are divided into one thousand chapters. In ancient times, Brahma imparted the knowledge of Ayurveda to Prajapati, who in turn taught it to the twin Ashwini Kumar, who passed on this knowledge to Indra, from whom Bhardwaj was taught and who then eventually brought the knowledge of Ayurveda to earth. Bhardwaj also imparted the knowledge of Ayurveda to Aterya and other sages who later shared their knowledge to their respective disciples.

Until this period, Ayurveda was compiled in a unified form; later on, due to the constraints of time and the deterioration of life span and intellect, eight separate branches were formed together with the formation of the different Schools of thoughts and treatises in their respective branches. All the three major authorities of Ayurveda Charaka, Sushruta and Vagbhata agree on these eight branches of Ayurveda with minor differences to their classification and order. These eight branches are:

Shalya : Tantra Surgery
Shalakya Tantra : ENT, Ophthalmology and Head, Neck & Fac
Kaya Chikitsa : Internal Medicine
Bhuta : Mental disorders
Kaumara Bhriya : Gynecology, obstetrics and Pediatrics
Agad Tantra : Toxicology
Rasayan Tantra : Geriatrics
Vajikarna : Andrology and sexology

Branch I : Shalya Tantra

The word Shalya means everything that bothers the psyche and/or soma. While defining Shalya Tanta Sushruta (Su. 1/8) states that Shalya Tantra (surgery) is the branch of Ayurveda which employs Yantra (blunt surgical instruments and tools) Shastra (sharp surgical instruments) Kshara (caustic bio chemical substances), Agni (cauterization) to extract various types of foreign bodies such as grass, wooden splinters, stones, minute particles, metal pieces, lumps, bones, hairs, nails, pus, exudate, abnormal foetus, etc. as well as the study of Vrna (traumatic wounds including inflammation).
Shalya Tantra incorporates the specialty of surgery.

Branch II : Shalakya Tantra

The term Shalakya is derived from the term Shalaka, which means a lancet or probe, implying that the branch of Ayurveda employing the usage of lancet and probe for the management of disease is Shalakya Tantra. In a true sense, though, the scope of Shalakya Tantra is much more than this. According to Sushruta, Shalakya Tantra encompasses the management of the clavicle bone. The specialties of ENT and ophthalmology are included in Shalakya Tantra.

Branch III : Kaya Chikitsa

The word Kaya means body. Another meaning of Kaya is Agni (internal fire). Therefore, Kaya Chikitsa means the management of the disorders of internal fire as well as the body. Defining the scope of Kya Chikitsa, Sushruta states that – the branch of Ayurveda which deals with the management of the disease such as Jwara (fever), Raktapitta (Bleeding dyscrasias, Hemophilia, etc.) Shosha (phthisis), Unmada (mania), Apasmara (epilepsy), Kustha (skin disorders) Prameha (urinary disorders), Atisara (diarrhea) etc, occurring in the whole of the body, is Kaya Chikitsa. The specialties of general medicine, pathology, cardiology, neurology, etc are also included in Kaya Chikitsa.

Branch IV : Bhuta Vidya

The word Bhuta means that which came into existence, but over the years the word has been used in connection with ghosts and other supernatural beings. Sushruta also states that Bbhuta Vidya is - the branch of Ayurveda which advocates the use of Shanti karma (appeasement rituals), Bali (sacrifice), etc. to rectify the problems arising out of the harmful influence of supernatural entities.

While discussing the manner of influence of these supernatural entities, Sushruta, further states that these entities do not themselves enter into a person but rather, innumerable followers of the particular entity enter the body of a person and accordingly produce signs and symptoms. This discussion brings into sharp focus, the school of thought which equates the concept of Bhuta with that of mental disorders. Thus the specialty of psychiatry is included under Bhuta Vidya.

Branch V : Kaumarabhritya

The literal meaning of the word Kaumarabhritya is the Nurturing of Kumara (Child) but in fact comprises much more. According to Sushruta, Kaumarabhritya is that branch of Ayurveda which deals with the management of Nurturing of Kumara, rectifying the problems of the mother's breast milk i.e. Dhatri, as well as other diseases of infancy and childhood. Subsequently, the Kumara Bhritya branch has come to encompass specialties of gynecology and obstetrics together with pediatrics.

Branch VI : Agada Tantra

In general the word Agada means disease, thereby implying that Agada means without disease, but in particular the word Agada stands for "Anti-poison". Sushruta defines Agad Tantra as the branch of Ayurveda which deals with the management of disorders arising out of the bites from snakes, insects, spiders, rats and other vermin, as well as the effects of various venoms and poisons. Agada Tantra incorporates the specialty of toxicology.

Branch VII : Rasayana Tantra

Chakra defines Rasayana as the measures adopted to achieve the best quality of Dhatus (body tissues). Sushruta defines Rasayana Tantra as that branch of Ayurveda which deals with the measures to check the effects of aging as well as to increase life span and memory. In the process, there may also be results in the improvement of diseases. Rasayana Tantra, therefore, is a specialty essentially dealing with the management of the phenomena of aging (Geriatrics).

Branch VIII : Vajikarana Tantra

The literal meaning of the word Vaji is stallion, thereby implying that Vajikarana means the process of metamorphosis of an ordinary man into a stallion especially in terms of his sexual power. According to Sushruta a Vajikarana Tantra is that branch of Ayurveda which deals with the management of the various disorders of Retas (semen). Broadly speaking, Vajikarana Tantra incorporates the speciality of Andrology and Sexology.