Mana refers to a supernatural force said to exist within all things, sometimes associated with maternal or lunar magic in mythology.
The word originates in Polynesian religion, and its modern use is a result of the popularization of the concept by anthropology and, to a great extent, by certain varieties of fantasy fiction. In Polynesian culture (e.g., Hawaiian, Māori), mana is analogous to respect, but it combines elements of respect, authority, power, and prestige. To have mana is to have influence and authority. This property is not limited to persons—peoples, governments, places, and inanimate objects can possess mana. In Hawaiian, mana loa means great power or almighty.
The word mana is also found in Norse mythology, and it is at least in part to this source that we owe its modern use. However, in Norse mythology, mana was restricted to the vital life-essence of all that was good; i.e., love, harmony, etc. It was believed to be the source tapped into to perform white magic.
The concept of mana has been, in various other cultures, the power of magic; however, it was not the only principle, and others included the concept of sympathetic magic and seeking the intervention of a specific supernatural being, whether deity, saint, or deceased ancestor.
The magic of mana was embedded into all talismans and fetishes, whether devoted to ancient gods, Roman Catholic saint relics, the spirits of the ancestors, or the underlying element that makes up the universe and all life within it. The concept of mana has been used in various cultures to justify human sacrifices, as the lives or blood of sacrificial victims might contain supernatural powers whose offering would please a deity.
Related cultural concepts
The concept of a life-energy inherent in all living beings seems to be a fairly universal archetype, and appears in numerous ancient religions and systems of metaphysics (in addition to having been borrowed by George Lucas's science-fiction films).
Analogies to mana in other societies include:
Also related are the philosophical concepts of:
The Polynesian word "mana" is not to be confused with the Hebrew "manna", which (according to the Bible) is a mysterious substance provided miraculously by God to the Hebrews in the desert. Some modern critics believe this may have been an edible wafer or sap of a variety of cactus found in the Sinai peninsula. Christian use of the word "manna" in reference to this, according to some, is thus unrelated to the Polynesian concept of "mana" (although there are definite archetypal similarities). "Man hu", or "manna" in the Hebrew language is translated as "what is it", and is likely only a phonetical coincidence with mana.
Political use of the term mana
The word Mana is found in the names of several political parties promoting Polynesian causes, notably the two New Zealand political parties Mana Motuhake and the Mana Maori Movement.
Mana in fictional works
In some fantasy settings and games (in particular role-playing games), "mana" is a natural energy resource which is used or channeled by wizards to cast magic spells. This use of the term was coined by Larry Niven in his 1978 novella, The Magic Goes Away, which deals with mana as a limited natural resource, becoming depleted. The use of the word outside of anthropological circles may well derive from this. (See magic point for more on mana in games.)
In J. R. R. Tolkien's universe, mana is a Quenya word believed to mean "what is". 
Mythology and religion: Inua, Sila, Magic Polynesian mythology, Honor, Animatism, Egyptian soul, Ark of the Covenant, Ten Commandments, Elemental, Sacrifice, Great Apostasy, Oloddumare
Other unrelated uses of the word mana include: