Prāṇāyāma is one of the eight limbs of Aṣṭāṅga Yoga, as propounded by Sage Patañjali. The word itself, is a compound word comprised of two Sanskrit words, prāṇa and āyāma. The words are loosely translated to life-breath (prāṇa) and elongation/control (‘āyāma.) Several explanations are offered in the Upaniṣads and Purāṇas, for the word ‘Prāṇa.’ Amongst the senses attached to this word are vital breath, energy, and embodiment of the Supreme. The Liṅga Purāṇa explains the word prāṇa as the vital breath that resides in the body – ‘प्राणः स्वदेहजो वायुः.’
The Nirvāṇa Prakaraṇa of Yogavāsiṣṭa states,
प्राणोऽयमनिशं ब्रह्मन्स्पन्दशक्तिः सदागतिः।
स बाह्याभ्यन्तरे देहे प्राणोऽयमुपरि स्थितः॥
prāṇo’yamaniśaṃ brahmanspandaśaktiḥ sadāgatiḥ।
sa bāhyābhyantare dehe prāṇo’yamupari sthitaḥ॥
[Yogavāsiṣṭa, 6.25.3]
That which moves incessantly within and without is Prāna. Within, it animates the body it pervades.
The word ‘āyāma’ means restraint or elongation. The Nārada Purāṇa states, ‘prāṇa is the vital breath that rests within the body, and the control of this breath is known as āyāma – प्राणो वायुः शरीरस्थ आयामस्तस्य निग्रहः।‘
The Mārkaṇḍeya Purāṇa summarizes the significance of Prāṇāyāma thus –
The Mārkaṇḍeya Purāṇa explains the significance of Prāṇāyāma as:
यथा पर्वतधातूनां ध्मातानां दह्यते मलम् ।
तथेन्द्रियकृता दोषा दह्यन्ते प्राणनिग्रहात् ॥
yathā parvatadhātūnāṃ dhmātānāṃ dahyate malam ।
tathendriyakṛtā doṣā dahyante prāṇanigrahāt ॥
[Mārkaṇḍeya Purāṇa, 30.10]
Just as metallic ore is purified to metal upon smelting, so too is man purified of impurities arising from absorption in the senses by the practice of Prāṇāyāma.
Maharṣi Patañjali states in his Yoga Sūtras, ‘with the proper practice of Prāṇāyāma that culminates in the utmost suspension of breath, the Yogi’s mind becomes free of wavering thoughts. He recognizes the pristine nature of the mind.’ With continued practice, Maharṣi concludes,
ततः क्षीयते प्रकाशावरणम् ।
tataḥ kṣīyate prakāśāvaraṇam।[2.52]
the veil which obscures the light of discerning knowledge is lifted.
P.S: It is advisable to practice Prāṇāyāma under the guidance of a spiritual master.