The nāḍīs are the subtle channels through which prāṇa moves, said to number many thousands. Three are principal: the central suṣumnā and the iḍā and piṅgalā on either side, associated with the moon and sun. Breath control and other practices aim to purify them and turn the flow of energy into the central channel.
Nāḍī
A channel of the subtle body through which vital energy flows.
Also: Nadi