The Sanskrit word Pranayama stands for “control of life force.” Made up of the words Prāna (life force) and āyāma (to restrain or suspend).
Most yoga scholars translate the word as meaning to control the force of your life with the help of your breath. During yoga practice pranayama is used to control the breathing in order to still the mind and to bring vital force to every cell of your body.
Yoga works primarily with the energy in the body, through the science of pranayama, or energy-control. Prana means also ‘breath.’ Yoga teaches how, through breath-control, to still the mind and attain higher states of awareness. The higher teachings of yoga take one beyond techniques, and show the yogi, or yoga practitioner, how to direct his concentration in such a way as not only to harmonize human with divine consciousness, but to merge his consciousness in the Infinite. – Paramahansa Yogananda