**2. Traditional medicine and Indian Systems of Medicine (ISM)**

The term "traditional medicine" (TM) refers to the ways of protecting and restoring health that existed before the arrival of modern medicine [7]. It incorporates plant, animal and mineral-based medicines, spiritual therapies and manual techniques designed to treat illness or maintain wellbeing [8, 9]. Many rural and ethnic communities in India use their indigenous knowledge for the treatment of various kinds of ailments [10]. They form the unwritten repository of health practices that have been verbally passed on to the next generations for at least one century and continue even today [11]. The World Health Organization (WHO) has also recognized the important role of traditional medicine in developing countries. WHO accepts that traditional medicine will continue to play an important part in providing services to very large number of people, particularly in rural areas [12].

India is a repository of vast traditional knowledge and a deep rooted system of indigenous medicine. According to a report from Government of India, about 75% of Indian population including majority of tribal and ethnic communities are mostly dependent on the traditional knowledge and practices for primary health care needs [13]. The system of medicines which are considered to be Indian in origin or the systems of medicine, which have come to India from outside and got assimilated in to Indian culture are known as Indian Systems of Medicine [14]. The age old Indian traditional medicine system "*Ayurveda*" is very extensive in terms of the plants used, owing to the great phytodiversity of the country. In addition, it is unique in having a well-defined conceptual framework which identifies it from many other traditional medicine systems [15]. In India, there are five recognized systems of medicine namely *Ayurveda, Yoga and naturopathy, Unani, Siddha and Homeopathy* (AYUSH).

The source of knowledge inculcated in *Ayurveda* finds its roots in one of the four ancient Indian texts (Veda), *Atharvaveda* which includes 114 hymns for prevention, treatment and cure of various diseases [14]. Two major written records of *Ayurveda* are *Charak Samhita* (for medicine) and *Shushrut Samhita* (for surgery). The fundamental principle of Ayurveda is to consider the physical and psychological status of body for maintaining healthy condition. It suggests ways to for proper life style and living in harmony with the nature. In Southern part of India, Siddha system of medicine is practiced. It has a close connection with the Tamil civilization and hence especially popular in Tamil Nadu. The experts of this medicine system are called *Siddhars* that means they have achieved excellence in this system of medicine. The siddha system of medicine uses drugs of metal and mineral origin to a large extent and with time it has included drugs of different other systems. The Siddha system resembles with Ayurveda as far as treatment procedures are concerned. The *Unani* system of medicine originated in Greece, established by Greek philosopher Hippocrates. This system of medicine was introduced in India by the Arabs. Homeopathy was brought to India in the 18th Century, however, it has been very well received by Indians and made a part of Indian System of Medicine.
