Genius

Genius comes from the Arabic word jinn which means spirit.

A genius is a person with distinguished mental prowess. This can manifest either as a foremost intellect, or as an outstanding creative talent. The IQ of a genius is usually defined as 140 or above. The term also applies to one who is a polymath, or someone skilled in many mental areas. The term specifically applies to mental rather than athletic skills, although it is also colloquially used to denote the possession of a superior talent in any field; e.g., Pelé may be said to have a genius for soccer or Gandhi for diplomacy.

Etymology
In Ancient Rome, the genius was the guiding or "tutelary" spirit of a person or indeed of an entire gens. A related term is genius loci, the spirit of a specific locale. In contrast, the internal driving force within all living things is the animus. A specific spirit, or daemon, may inhabit an image or icon, giving it supernatural powers.

A comparable term from Arabic lore is a djinn, often Anglicized as "genie". Note, however, that this term is a false friend, not a cognate.

Gifted
Geniuses come gifted with phenomenal brilliance, they are often as insensitive to the limitations of mediocrity as they may be very sensitive emotionally themselves, sometimes both. The term prodigy simply denotes the presence of exceptional talent or genius in early childhood. The terms prodigy and child prodigy are synonymous, the latter being a pleonasm.

Artistic genius may show itself in early childhood (prodigy) or later in life; either way, geniuses eventually differentiate themselves from the rest through great originality. Intellectual geniuses usually have crisp, clear-eyed visions of given situations, in which interpretation is unnecessary—the facts just hit them, and they build or act on the basis of those facts, usually with tremendous energy. Here too, accomplished geniuses in intellectual fields start out in many cases as prodigies, gifted with superior memory, pattern recognition or just understanding.

The classical skill of the musical genius is the capability of holding many different melodies in one's head at once and knowing how they interact together. In the classical greats (Bach, Mozart, etc) you can hear and read about them holding 5, 6 and even 7 different melodies in their head at once. They could just write music, all of it, at once without having to hear it played. In comparison, the average person can hold 1 melody in memory.

A theory put forth by Harvard professor Howard Gardner in his 1983 book Frames of Mind states there are seven kinds of intelligences, each with its own type of genius. See theory of multiple intelligences for more on this view.

Intelligence is exceptionally difficult to quantify. The standard measurement in the United States is by the I.Q. test. This is criticized by many as it only measures some aspects (some argue an ethnocentric and academic aspect) of intelligence.

Limitations
Geniuses are often accused of lacking common sense. Stories of a genius in a given field being unable to grasp "everyday" concepts are abundant and of ancient vintage: Plato in the Theaetetus (dialogue) offers a picturesque anecdote of the absentmindness of Thales. Einstein reportedly sawed the rudder off his sailboat while at sea. A genius's intense focus on a given subject might appear obsessive/compulsive in nature, but it might also simply be a choice made by the individual. If one is performing groundbreaking work in one's field, maintaining other elements of life might logically be relegated to insignificance. While the absent-minded professor notion is not without merit, a genius is just as likely to encounter emotional problems as anyone else. Note the peculiarities of figures like Glenn Gould and Bobby Fischer. Such examples, however, are likely products of mental or emotional instability rather than genius per se, though there is a researched correlation between I.Q. and maladjustment.

Socio-emotional problems are more prevalent in geniuses with an IQ above 145. There are several reasons why scientists believe this. Asynchronous development and obtuse relationships of children is one notable reason explaining such maladjustedness. The single greatest adjustment problem of the gifted is the tendency to become isolated from others. As these children do not share other children's interests, vocabulary, or desire to organize activities, the genius child may withdraw. The gifted are not likely to fall victims to positive suggestion but many develop negativism to a conspicuous degree.

Some research shows that reasons other than maladjustment make companionship difficult to find for geniuses. As intelligence of a person increases, what they consider as their peers constitutes a shrinking number of people. For example, at an IQ of 135 only every hundredth person would be of equal or greater IQ. This number shrinks significantly as IQ goes up.

Leta Hollingworth implied the idea of a "communication range" for geniuses. Observation shows that there is a direct ratio between the intelligence of the leader and the led. To be a leader of his contemporaries a child must be more intelligent but not too much more intelligent than those to be led. This implies that geniuses make better leaders and that they could have disdain for authority. The theory goes on to state that children and adults become intellectually isolated from their contemporaries when an IQ difference of 30 points exists. 

It is important to note that some social and economic factors can prevent expression of genius. Such factors include societal expectations of women and repression of minorities. For this reason, apparent male-bias and European-bias among the past and current geniuses of the world may not indicate an actual difference in the incidence of biological geniuses from other groups.

In philosophy
In the philosophy of Arthur Schopenhauer, a genius is a person in whom intellect predominates over will much more than for the average person. In Schopenhauer's aesthetics, this predominance of intellect over will allows the genius to create artistic or academic works that are objects of pure, disinterested contemplation, the chief criterion of the aesthetic experience for Schopenhauer. Their remoteness from mundane concerns means that Schopenhauer's geniuses often display maladaptive traits in more mundane concerns; in Schopenhauer's words, they fall into the mire while gazing at the stars.

In the philosophy of Immanuel Kant, genius is the ability to independently arrive at and understand concepts that would normally have to be taught by another person. In the Kant Dictionary (ISBN 0-631-17535-0), Howard Caygill talks of the essential character of "genius" for Kant being originality. This genius is a talent for producing ideas which can be described as non-imitative. Kant's discussion of the characteristics of genius is largely contained within the Critique of Judgement and was well received by the romantics of the early 19th century.

Pluralization
In this context, the plural of "genius" is "geniuses." The form, "Genii," while intuitive given words such as "cactus" (pluralized as "cacti"), is the plural of a different kind of genius: the aforementioned guardian spirit of Roman mythology.