The word nadi means 'flow'. In this sense, nadis are subtle flows of energy, just as electricity, radio waves and laser beams are subtle flows.
Nadis are pathways of pranic, mental and spiritual currents, which form a matrix throughout the physical body. They provide energy to every cell, organ and part through their vast network, carrying prana back and forth in every direction. Nadis are not physical, measurable or dissectible structures within the body, but channels of energy which underlie and sustain life and consciousness.
They can be perceived at the psychic level as distinct channels of light, colour and sound.

Ancient books on yoga says there are 72,000 of nadis emerge from navel centre.
Out of the thousands of nadis, which include all the major and minor flows, 72 are considered important. Out of these 72, ten nadis- ida, sushumna, pingala, gandhari, hastijihva, yashaswini, pusha, alambusha, kuhu and shankhini are considered to be major. Among these 10 nadis, three are most significant: ida, pingala and sushumna. These three major nadis are situated in the spinal column and pass through every chakra and they govern the whole system of the nadis and all the body processes.

Ida nadi is the mental channel, pingala nadi the vital channel and sushumna nadi the spiritual channel. Ida, pingala and sushumna are the three main channels for the distribution of energy throughout the entire pranic network. They are the high voltage wires that conduct the energy from the sub-stations or chakras situated along the spinal column to all the other nadis.

Ida is also known as the chandra, or lunar channel and Pingala as the surya, or solar channel. Ida and pingala indicate time, while sushumna is the devourer of time, since it leads to timelessness or eternity.

All the three channels originate from mooladhara chakra. Ida and pingala flow alternately, coiling around the spinal passage from left to right, while sushumna flows straight up through the middle. The central axis of ida and pingala is sushumna. This nadi is the mystical path of yoga that flows in between ida and pingala. Sushumna rises straight up through the centre of the spine, meeting ida and pingala at the points where they cross the chakras, and uniting with them at ajna chakra (third eye centre).

Sushumna is the pathway through which the kundalini rises, and thus forms the basis for the progressive awakening of higher knowledge. However, this pathway remains dormant in most people until a higher state of evolution is reached.

Pingala represents the positive polarity and is the solar force. Physical vitality, dynamic activity and tension are qualities of pingala energy. It is hot in nature and corresponds to the sympathetic nervous system.
Ida represents the negative polarity and is the lunar force. It is cold in nature and corresponds to the parasympathetic nervous system. Relaxation, passivity and sedentary activity are qualities of ida.

Pingala represents the positive polarity and is the solar force. Physical vitality, dynamic activity and tension are qualities of pingala energy. It is hot in nature and corresponds to the sympathetic nervous system.
Ida represents the negative polarity and is the lunar force. It is cold in nature and corresponds to the parasympathetic nervous system. Relaxation, passivity and sedentary activity are qualities of ida.

When sushumna is active, the breath flows through both nostrils simultaneously. Sushumna flows after practising pranayama, prayer and meditation. When sushumna flows, the whole brain operates, but only half of the brain is active during the flow of ida or pingala.

Keep practising yoga & Pranayama!
Hari AUM