Yoga (Sanskrit: योग|योग), comes from Indian philosiphy, which means "union". It is aimed at achieving the union of individual soul with the universal. Through systematic excercises of body and mind, it encourages the union of mind, body and the spirit. A practitioner of Yoga is called a Yogi (male) or Yogini (female). Many Hindu texts discuss aspects of yoga, including the Vedas, Upanishads, the Bhagavad Gita, the Yoga Sutras of Patanjali, the Hatha Yoga Pradipika, the Shiva Samhita and various Tantras. Classified by the type of practices, the major branches of yoga include: Hatha Yoga, Karma Yoga, Jnana Yoga, Bhakti Yoga, and Raja Yoga. The philosophy of hatha yoga, established by the Yoga Sutras of Patanjali, and known simply as yoga in the context of Hindu philosophy, is one of the six orthodox (āstika) schools of thought.
The Sanskrit term yoga has many meanings. There is a list of 38 meanings of the word "yoga" . It is derived from the Sanskrit root yuj, "to control", "to yoke", or "to unite" . Common meanings include "joining" or "uniting", and related ideas such as "union" and "conjunction" . Another conceptual definition is that of "mode, manner, means".
Concepts and Principles
The tradition of Yoga was born in India several thousand years ago. Great Saints and Sages were the founders of yoga. The great Yogis gave rational interpretation of their experiences about Yoga and brought a practically sound and scientifically prepared method within every one’s reach. Yoga philosophy is an Art and Science of living in tune with Brahmand- The Universe. Yoga has its origins in the Vedas, the oldest record of Indian culture. It was systematized by the great Indian sage Patanjali in the Yoga Sutra as a special Darshana. Although, this work was followed by many other important texts on Yoga, but Patanjali’s Yoga Sutra is certainly the most significant wherein no change is possible. It is the only book which has touched almost all the aspects of human life. 
Unlike earlier, Yoga today is no longer restricted to a privileged minority of hermits; it has taken its place in our every day lives and have undergone a world wide awakening and acceptance in the last few decades. The Science of Yoga and its techniques have now been re-oriented to suit modern sociological needs and lifestyle. Experts of various branches of medicine including modern medical science are realizing the role of these techniques in the prevention of disease and promotion of health. Swami Vivekananda defines Yoga as "It’s a means of compressing one’s evolution into a single life or a few months or even a few hours of one’s bodily existence". By Yoga, Sri Aurobindo, meant a methodological effort towards self perfection by the development of potentialities latent in the individual.
Yoga is a science as well an art of healthy living physically, mentally, morally and spiritually. It’s systematic growth from his animal level to the normalcy, from there to the divinity, ultimately. It’s no way limited by race, age, sex, religion, cast or creed and can be practiced by those who seek an education on better living and those who wants to have a more meaningful life. Yoga is not a religion; It’s a philosophy of life based on certain psychological facts and it aims at the development of a perfect balance between the body and the mind that permits union with the divine i.e. perfect harmony between the individual and the cosmos. Many different interpretations of the word Yoga have been handed down over the centuries. One of the classic definition of Yoga is "to be one with divine." It does not matter what name we use for the divine-God, Allah, Ishvara, or whatever- anything that brings us closer to understanding that there is a power higher and greater than ourselves is Yoga. When we feel in harmony with that higher power, that too is Yoga.
Yoga is one among the six systems of Indian orthodox philosophy. Maharishi Patanjali, rightly called as the "Father of Yoga" compiled and refined various aspects of Yoga systematically in his "Yoga Sutras" (aphorisms). He advocated the eight fold path of Yoga, popularly known as "Ashtanga Yoga" for all-round development of human personality. They are – Yama, Niyama, Asana, Pranayama, Pratyahara, Dharana, Dhyana & Samadhi. These eight limbs are so perfectly designed that there is absolutely no scope for any addition or alteration since these are formulated on the basis of multifarious psychological understanding of human personality. The practice of Yamas – Niyamas i.e. harmlessness towards all living beings, truthfulness, honesty, celibacy, non-hoarding of wordly objects, cleanliness, contentment, austerity, control of lust, anger and infatuation, study of holy books and practice of Japa and selfless action – all these pave way for increasing the power of concentration, mental purity and steadiness.
Svatmarama, who wrote a treatise on this subject after experiencing the nectar of samadhi (absorption of the soul) as Hatha Yoga Vidya or Hatha Yoga Pradeepika. It gives guidelines from the practical point of view for a beginner to begin Yoga, which leads the students gradually from the culture of the body towards the sight of the soul and God-realisation. Hatha Yoga Pradeepika is divided into four chapters or Prakaranas. The first chapter expounds Asanas, the second is on pranayama, the third is on Mudras and Bandhas and the fourth is on Pratyahara, Dharana, Dhyana and samadhi. In between these, the author introduces satkriyaas or the six cleansing processes. As the text begins with asanas, Satmarama’s Yoga is called Sadanga Yoga or the six aspects of Yoga beginning with asanas and ending in Samadhi. A set of Asanas, Mudras and Pranayamas practised with faith, preseverance and insight rejuvenates the brain, heart, lungs, liver, pancreas, kidneys, bowels, nerves, muscles, tissues & glands of the body by ensuring oxygenated and balanced blood supply, kindles up the appetite, bestows control over seminal fluid, senses & mind and imparts increased vitality, vigour & longevity to the practitioner.
Streams of Yoga
There are a large numbers of methods of Yoga catering to the needs of different persons in society. They are broadly classified into four streams. Swami Vivekananda puts them as Work, Worship, Philosophy and Psychic control. Karma Yoga, the path of work, involves doing action in a skilful way. In other words, it can be said as a way of enjoying work, doing it effortlessly. The success or failure should not be allowed to cause ripples in the mind. ‘Bhakti Yoga’ the path of worship is a systematic method of engaging the mind in the practice of divine love. This attitutde of love softens our emotions and tranquillises our mind. Jnana Yoga, the path of philosophy, is a systematic way of tutoring the mind about the realities of life by contemplation. This will strip off the garb of Avidya (ignorance) from our mind and the mind goes to its natural state of rest. Raja Yoga, the path of psychic control, is a systematic process of culturing the mind. It is based on the 8-limbed Yoga of Patanjali. Yoga is a science as well as an art of healthy living. It is no way limited by race, age, sex, religion, caste, creed and any other boundaries and can be practiced by those who seek an education on better living and those who want to have a more meaningful life.
Yoga means a holistic approach towards the cause and treatment of disease. According to Yoga, most of the diseases Mental, Psychosomatic and Physical originate in mind through wrong way of thinking, living and eating which is caused by attachment. The basic approach of Yoga is to correct the life style by cultivating a rational positive and spiritual attitude towards all life situation. Yoga does not treat gross body alone, it takes into consideration all the five Kosa’s (Sheaths) i.e. Manomaya Kosa, Annamaya Kosa, (grass Sheath) Pranamaya Kosa (Extral Body) (Psychic Body), Vijyanmaya Kosa (intellect Sheath) and Anandamaya Kosa (Bliss sheath). Like Ayurveda and Naturopathy Yoga also takes up the cleansing of the body as the first measure to fight disease. While Ayurveda performs its pancha karma through the help of ametics purgative Yoga performs them without the help of any drug i.e. by developing full efficiency and control of eliminative systems of the body. Which no other system of health care can do.
All the systems of medicine at their best aim at curing the disease whereas Yoga aims at preventing the disease and promoting health by reconditioning the psycho-physiological mechanism of the individual. Yoga emphasises the development of brotherhood, hormony, fraternity and equality not only towards all human beings irrespective of colour, caste, nationality, age and sex but towards all living beings also. This attitude renders the thinking so positive that man is liberated from all mental malice and also all the mental, psychosomatic and physiological diseases arising thereof. The approach of Yoga is not confirmed to various disorders, it aims at bringing under perfect control of the mind, senses and pranic energy and direct them towards healthier channels with a view to aquire mental purity, intellectual stability and spiritual bliss. Yoga is very wide and comprehensive system embracing all walks of human life. It is unlike Ayurvedic, Unani and Homoeopathy. It is not merely a system of treatment but has potential to develop alround health i.e. physical, social, mental and spiritual. For social health, it prescribes the practice of Yama & Niyama and Karma Yoga. A man devoted to karma Yoga looks all the living beings as his bretherens and helps them getting rid of painful situations. This concept of "Vasudhaiv Kutmba Kama" is the basic Philosophy of Yoga.
Yoga emphsises the practitioners to withstand the environmental influences both external & internal as well as physical & mental processes. This practice cultivates strong immunity in them and make them capable of offering a effective ressistance to various environmental pressures and thus, maintains behavioural equanimity and intellectural stability. The practice of Yama – Niyamas purifies the heart of practitioner from vices like attachement, aversion, avarice and infatuation etc. and generates higher ethical qualities like sincerity, honesty, straightforwardness, cheerfulness, courage, detachement, patience, perseverence, tranquility, self conrol, truth, harmony and uprightness. Our ancient seers have very sagaciously designed the Yogic practices to invigorate the entire psychosomatic consitution of man. A set of Asanas, Mudras and Pranayamas practised with faith, perseverance and insight rejuvenates the brain, heart, lungs, liver, pancreas, kidneys, bowels, all nerves, muscles, tissues, glands of the body by ensuring oxygenated and balanced blood supply, kindless up the appetite, bestows control over seminal fluid, senses and mind and imparts increased vitality, vigour and longevity to the practitioners.
Yoga Develoment and its Status
In India, generations of Yogis and Scholars have contemplated their life in timeless fashion to realize that there is a meaning to life and some purpose beyond the human sufferings. They were even convinced that there is a way to escape the tragic problems of life by diverting our mind to something more interesting and everlasting. They were also moved by the suffering they saw around them and wanted that the human being should be free from sufferings & ignorance, to set him on the road to freedom and live healthy . In ancient days, most of the Yogis & Sages used to live in forests. They use to eat whatever is provided by the Nature in its natural form. Not only that the ever changing climate could not harm them a bit. They use to apply holy ash of Havana on their body to keep away the germs & bacteria. The great Yogis and Scholars gave rational interpretations of their experiences and brought these within every one’s reach by making a practically designed and scientifically prepared method of healthy living. Hence, the science of Yoga emerged to counter all these problems and human sufferings. In the ancient days, Medicine was dominated by magical and religious beliefs which were an integral part of almost all ancient cultures and civilizations. Although primitive man may be extinct, his progeny - the so called " Traditional Healers " , are found everywhere. They live close to the people and their treatment are based on various combinations of religion, magic and empiricism.
The greatest Physician in Greek medicine was Hippocrates, who is often called the "Father of Medicine". He studied such things as climate, water, air, clothing, habits of eating & drinking and the effect they have in producing diseases. The Greeks believed that matter was made up of four elements - Earth, Air, Fire, Water and the same is applicable to body also. They also believed that the equilibrium among these elements maintains normal health status. Medicine has moved from organism to organ and from organ to cell and from the cell to molecular properties. Despite spectacular bio-medical advances and massive expenditures, the death rate and the life expectancy in the developed countries have remained unchanged. Medicine, as practiced today has begun to be questioned and criticised. High technology medicine seems to be getting out of hand and leading health systems in wrong directions. There is an increasing concern about the cost and allocation of health resources, but the efficacy of modern medicine is fundamentally questioned through various points of view. Contemporary medicine is no longer solely an art and science for the diagnosis and treatment of diseases. It is also the science for prevention of disease and promotion of health. With increasing recognition of the failure of existing health services to provide health care, alternative ideas and methods to provide health care have been considered and tried in large scale in the recent past.
The sacred land of India, from the time immemorial contributed in its own way to the better living of mankind. Yoga & Naturopathy are the two of its kinds which can be the only answer to the rising levels of health care problems. In recent times there is a growing awareness among the people about the efficacy and utility of Yoga and Nature Cure in keeping one fit at physical, mental, emotional, social and spiritual planes. These systems are emerging as the effective methods and means to improve the total personality and to build a healthy society. Above all, these systems are adopted as a way of life rather than a mode of treatment.