Pranayama
प्राणायाम (prāṇāyāma)
The regulation of breath - yoga's fourth limb, extending and refining the one trainable vital current. Read in English
प्राणायाम — श्वास का नियमन; योग का चौथा अंग, एकमात्र साधने योग्य प्राण-द्वार का विस्तार।
Pranayama joins prana with ayama - extension, restraint - and names the family of practices that work on the breath deliberately: lengthening it, balancing it, pausing it. In Patanjali's sequence it follows posture and precedes the inward limbs, a bridge between body and attention.
Modern physiology has caught up with pieces of it: slow exhalation engages the parasympathetic system; balanced nostril practices correlate with measurable shifts in arousal. The maps differ; the territory behaves.
The classical texts insist on gentleness - breath is forced at one's peril. For most people most days, the useful dose is humble: a few minutes of even, unhurried breathing with the exhale slightly long. As one teacher put it, first make the breath a friend; techniques come after the friendship.