तस्मिन्सति श्वासप्रश्वासयोर्गतिविच्छेदः प्राणायामः

tasmin sati svasaprasvasayorgativicchedah pranayamah

The next step is pranayama, regulation of inhalation and exhalation.

Yoga Sutras of Patanjali, 2.49

tasmin = upon that
sati = being accomplished
svasa = inhalation
prasvasayo = exhalation
gati = flow
vicchedah = cessation
pranayama = breath regulation

A simple calming breath practice I love to do is take two deep inhales and then one slow, long exhale.