Pra means “first unit” and na, “energy”. Prana is the energy which underlies all activity, physical and mental.
(Yoga and Psychotherapy p49 by Swami Rama)
The word Shakti comes from the root shak, meaning to have power or to be able.
The other part of this polarity is a dynamic, energetic, or creative aspect that is called Shakti, the great mother of the universe, for it is from her that all form is born. Shakti is the subtlest of created things. She manifests herself as the entire universe including matter, life, and mind.
Kundalini is the Divine Cosmic Energy in bodies.
The dynamic energy that provides the working forces for the body evolves from the active energy of Shakti and is called prana. Electrical energy is more subtle than mechanical energy. Its properties have come to be recognized and utilized in the past two hundred to three hundred years. Before that the idea of electrical forces was quite foreign to the thinking of most people. This is the situation today with our empirical understanding of prana. Prana is a still more subtle form of energy that is not yet studied or understood in the mainstream of modern science. However, it has been studied in detail in the introspective science of yoga.
Prana is organized and subdivided according to specific functions in the body.
(Inspired Thoughts of Swami Rama p213 by Swami Rama)
Prana indicates not only the energy which supports the activities of the body fundamentally, but also the energy of the whole universe (Shakti).
You will be able to realize what the whole universe is by realizing every prana permeating everywhere.
Nahna called the subtlest and purest energy that is the source of the creative whole universe (Shakti) “Pranahna”.
“Pranahna” is prana, the essential energy flowing out of Nahna. (Nahna)