In popular usage, eccentricity refers to unusual or odd behavior on the part of an individual. This behavior would typically be perceived as unusual or unnecessary, without being demonstrably maladaptive. Eccentricity is contrasted with "normal" behavior, the nearly universal means by which individuals in society solve given problems and pursue certain priorities in everyday life. People who consistently display benignly eccentric behavior are labelled as "eccentrics."

Depictions of eccentricity

Eccentricity is often associated with genius, giftedness, or creativity. The individual's eccentric behavior is perceived to be the outward expression of his or her unique intelligence or creative impulse. In this vein, the eccentric's habits are incomprehensible not because they are illogical or the result of madness, but because they stem from a mind so original that it cannot be conformed to societal norms. Edith Sitwell wrote:

"Eccentricity is not, as some would believe, a form of madness. It is often a kind of innocent pride, and the man of genius and the aristocrat are frequently regarded as eccentrics because genius and aristocrat are entirely unafraid of and uninfluenced by the opinions and vagaries of the crowd."

Comparison to the norm

A person who is simply in a "fish out of water" situation is not, by the strictest definition, an eccentric since, presumably, he or she may be ordinary by the conventions of his or her native environment.

Eccentrics may or may not comprehend the standards for normal behavior in their culture. They are simply unconcerned by society's disapproval of their habits or beliefs and most often display extreme individualism. Many of history's most brilliant minds have displayed many unusual behaviors and habits.

Some eccentrics are pejoratively considered "cranks", rather than geniuses. Eccentric behavior is often considered whimsical or quirky, although it can also be strange and disturbing. Many individuals previously considered to be merely eccentric, such as aviation magnate Howard Hughes, have recently been retrospectively-diagnosed as actually suffering from mental illness (obsessive compulsive disorder in Hughes' case). Probably the best example was Serbian-American physicist and inventor Nikola Tesla. Another famous eccentric was renowned theoretical physicist Albert Einstein; his eccentricities included picking up discarded cigarette butts off the street in order to circumvent his doctor's ban on buying tobacco for his pipe, piloting his sailboat on windless days ("for the challenge"), and lecturing his 8-year-old nephew on physics (including a 2-hour exposition on the Newtonian properties of soap bubbles).

Other people may have eccentric taste in clothes, or have eccentric hobbies or collections which they pursue with great vigor. They may have a pedantic and precise manner of speaking, intermingled with inventive wordplay.