Yoga is a family of ancient spiritual practices originating in India. Today in India and across the World, Yoga is a vibrant living tradition and is seen as a means to both physical health and spiritual mastery. Karma Yoga (yoga of Action), Jnana Yoga (yoga of Knowledge), Bhakti Yoga (yoga of Devotion), and Raja Yoga (yoga of Meditation) are considered the four main paths of Yoga

Outside India, Yoga has become primarily associated with the practice of asanas (postures) of Hatha Yoga a system of Yoga that developed from - and in order to prepare students for the practice of - Raja Yoga. The word "yoga" derives from the Sanskrit root yuj ("to yoke"); which is cognate to modern English "yoke". All derive from the Proto-Indo-European root *yeug- meaning "to join" or "unite". It is generally translated as "union of the individual atma (loosely translated to mean soul) with Paramatma, the universal soul." This may be understood as union with the Divine by integration of body, mind, and spirit.
 

The Bhagavad Gita talks of four branches of yoga:
(1) Karma yoga (sometimes called Kriya yoga), the yoga of action in the world
" With the body, with the mind, with the intellect, even merely with the senses, the yogins perform action toward self-purification, having abandoned attachment. He who is disciplined in yoga, having abandoned the fruit of action, attains steady peace..." (Ch5:V11-12)
   
(2) Jnana yoga, the yoga of knowledge and intellectual endeavor
" When he perceives the various states of being as resting in the One, and from That alone spreading out, then he attains Brahman. They who know, through the eye of knowledge, the distinction between the field and the knower of the field, as well as the liberation of beings from material nature, go to the Supreme." (Ch15:V31/35)
   
(3) Bhakti yoga, the yoga of devotion to a deity
".... those who, renouncing all actions in Me, and regarding Me as the Supreme, worship me... of those whose thoughts have entered into Me, I am soon the deliverer from the ocean of death and transmigration, Arjuna. Keep your mind on Me alone, your intellect on Me. Thus you shall dwell in me hereafter." (Ch12:V6-8) " And he who serves me with the yoga of unswerving devotion, transcending these qualities [binary opposites, like good and evil, pain and pleasure] is ready for absorption in Brahman." (Ch14:V26)
   
(4) Raja yoga, the yoga of meditation
" Establishing a firm seat for himself in a clean place... having directed his mind to a single object, with his thought and the activity of the senses controlled, he should practice yoga for the purpose of self-realization. Holding the body, head and neck erect, motionless and steady, gazing at the tip of his own nose and not looking in any direction, with quieted mind, banishing fear, established in the brahmacharin vow of celibacy, controlling the mind, with thoughts fixed on Me, he should sit, concentrated, devoted to Me. Thus, continually disciplining himself, the yogin whose mind is subdued goes to nirvana, to supreme peace, to union with Me." (Ch6:V11-15)
   

Principles of Yoga

Patanjali's Eight Principles of Yoga
(1) Yama (The five "abstentions or abstinence"): violence, lying, theft, (illicit) sex, and possessions
(2) Niyama (The five "observances"): purity, contentment, austerities, study, and surrender to god
(3) Asana: Literally means "seat", and in Patanjali's Sutras refers to seated positions used for meditation. Later, with the rise of Hatha yoga, asana came to refer to all the "postures"
(4) Pranayama ("Life Force Control"): Regulation of breath or control of prāna, life force, or vital energy
(5) Pratyahara ("Abstraction"): Reversal or withdrawl of the sense organs
(6) Dharana ("Concentration"): Fixing the attention on a single object
(7) Dhyana ("Meditation"): Intense contemplation of the true nature of reality
(8) Samadhi ("Liberation"): Super-conscious state of enlightenment
   

Swami Sivananda's Modified Five Principles of Yoga
1. Proper relaxation
Releases tension in the muscles
Helps letting go of all worries
Ensures conservation of energy
   
2. Proper exercise Yoga postures - to be performed as per body constitution.
Yogic consultation is a must.
Correct postures work systematically on all parts of the body. Stretching and toning the muscles & ligaments. Keeping the spine and joints flexible. Improving the blood circulation.
   
3. Proper breathing (pranayama)
Brings an extraordinary balance in the consciousness
Teaches you to control your mental state by regulating the flow of the life force.
   
4. Proper diet
Chart out a well-nourished balanced diet.
Keeps the body light and supple and the mind calm.
Resists ailments.
   
5. Positive Thinking & Meditation
Removes negative thoughts. Stills the mind.
You attain super-consciousness. A state beyond time, space and causation.