The word ‘yoga,’ comes from the Sanskrit root YUJ, ‘to join’, and means ‘unity’ or ‘union’. The great Sanskrit grammarian, Panini, who codified the language in the 4th century BC, tells us: ‘That which unites is called yoga.’ He defines the word in three ways: ‘union’ (samyoga), ‘coherence’ (sanyama) and ‘the unification of the individual mind with Universal Consciousness’ (samadhi).
....It was the great Vedic teacher, Patanjali, who defined the actual nature of yoga, probably in about the 3rd century BC. His Yoga Sutras and the many ancient commentaries on them are still an actively read part of the Hindu canon. Clearly, however, the teaching was an oral one long before it was written down for the sutras are more like lecture notes than scripture. The word ‘sutra’ means ‘thread’ and the brief aphorisms of the Yoga Sutras -- averaging only six words each -- are designed to be teased and unravelled into their full meaning through the application of the yoga techniques they describe.
....As a basis for the teaching of yoga, Patanjali established the ‘eight limbs of yoga’ (ashtavangani) to provide a basis for living. Not dissimilar from the Buddhist ‘Eight Fold Path’, the eight limbs of yoga are:

....The eight limbs of yoga have often been interpreted as sequential steps on the path to yoga.The first two limbs -- yama and niyama -- were seen as prerequites for the following six. In such a system, the reward of samadhi, the settled mind, would only be reached after years spent perfecting the preceding stages. Such an interpretation is perfectly understandable in the light of the Christian ethos, in which good action is rewarded. It is not, however, compatible with the main contention of the Vedas -- that everything is based in and on consciousness.
....The basis of any real practice of yoga is in the daily routine of asanas, pranayama and meditation. It is these that produce the state of samadhi. While it is true that the state of ultimate samadhi is not possible without the other seven limbs being fully developed, samadhi is not an absolute; it has many forms and comes in many flavours -- the most Divine being ‘the sweet taste of Soma’.
....The use by Patanjali of the word ‘anga’ -- ‘limb’-- to describe the parts of yoga is significiant and meaningful. The limbs of yoga are not separate but form the body of yoga. But at the heart of that body is the daily practice of asanas, pranayama and meditation and the samadhi it produces. Out of this practice, the body of yoga grows, as it should, spontaneously and by itself. No amount of conscious effort to practise non-violence, truthfulness, simplicity or contentment can produce the depth of meaning that such qualities require to make their fullest contribution to the Cosmic Order. These qualities, however, blossom and come to flower through the practise of right meditation.