noun

• The impetus behind all motion and all activity.
• The capacity to do work.
• (physics) A quantity that denotes the ability to do work and is measured in a unit dimensioned in mass × distance²/time² (ML²/T²) or the equivalent.
• An intangible, modifiable force (usually characterized as either 'positive' or 'negative') believed in some New Age religions to emanate from a person, place or thing and which is (or can be) preserved and transferred in human interactions; shared mood or group habit.
• (Eastern Orthodoxy, theology, often in the plural) The external actions and influences resulting from an entity’s internal nature (ousia) and by which it is made manifest, as opposed to that internal nature itself; the aspect of an entity that can affect the wider world and be apprehended by other beings.
• (roleplaying games, video games, board games) A measure of how many actions a player or unit can take; in the fantasy genre often called magic points or mana.
• (Internet slang) An atmosphere, aura, or vibe.