तस्मिन् सति श्वासप्रश्वासयोर्गतिविच्छेदः प्राणायामः

Tasmin sati śvāsa-praśvāsayor gati-vicchedaḥ prāṇāyāmaḥ

Pranayama is the regulationof the movement ofinhalation and exhalation.

The Definition of Pranayama