One of the three aspects of all things in nature: matter, energy, and consciousness.
In spirituality, energy is that which empowers action. There are many levels and types of energy, most of which are unknown to modern science.
From Greek energeia "activity, action, operation," from energos "active, working," from en "at" + ergon "work, that which is wrought; business; action." From Aristotle, the word was used with a sense of "actuality, reality, existence."
Equivilent in Sanskrit: shakti (energy, power) or virya (sexual virility, power).
In Hebrew, energy is מרץ, "energy, vigor, forcefulness," and is also the name of the planet Mars, which according to the Zohar is ruled by Samael, an angel whose name means "the medicine of God."
“Matter transforms into energy; energy transforms into matter.” - Einstein
“Energy and strength are necessary for all processes and all activities. The higher the activity, the greater the need of energy.” - Swami Sivananda
"Matter is nothing but condensed energy. The infinite modifications of energy are absolutely unknown, as much as for historic materialism as for dialectic materialism. Energy is equal to mass by the velocity of the light squared... Matter is condensed energy. When its vibration is very slow, its mass is beneath the limits of external sensorial perceptions. When its vibratory movement is very fast, then the mass is above the limits of external sensory perceptions. With the telescope, we can only see worlds whose degree of vibration is active within the limits of external sensory perception. Above and below the limits of external sensory perceptions there exist worlds, solar systems, and constellations populated by many types of living beings. The so-called matter is only energy that condenses into infinite masses. The senses of external perception only reach a fraction of what is perceivable." - Samael Aun Weor, Tarot and Kabbalah
"Within us there are various types of energy which we must understand: ￼￼￼￼￼￼￼￼￼First, mechanical energy; Second, vital energy; Third, energy of the psyche; Fourth, mental energy; Fifth, energy of the will; Sixth, energy of the consciousness; 2 Seventh, energy of the pure Spirit. No matter how much we might increase our ￼￼￼￼￼￼￼￼strictly mechanical energy, we will never awaken consciousness. No matter how much we might increase the vital forces within our own organism, we will never awaken consciousness. Many psychological processes take place within us without any intervention from the consciousness. However great the disciplines of the mind might be, mental energy can never achieve the awakening of the diverse functions of the consciousness. Even if our willpower is multiplied infinitely, it can never bring about the awakening of the consciousness. All these types of energy are graded into different levels and dimensions, which have nothing to do with the consciousness." - Samael Aun Weor, The Great Rebellion