This page refers to eccentricity in behavior and popular usage. For other uses, see the disambiguation page: eccentricity.

In popular usage, eccentricity refers to unusual or odd behavior on the part of a person, as opposed to being normal. Eccentric behavior is often considered whimsical or quirky, although it can also be strange and disturbing. American millionaire Howard Hughes, for example, was considered to be very eccentric in his old age, when he stored his urine in glass jars and never cut his hair or nails. Other people may have eccentric taste in clothes, or have eccentric hobbies or collections.

Many of history's most brilliant minds have displayed many unusual behaviors and habits, and eccentricity is sometimes thought to be a sign of genius. However, many eccentrics are cranks, rather than geniuses.

John Stuart Mill says in his philosophical work On Liberty that the existence of eccentricity within a society is not only possible, it is essential. This bohemian personage, similar to that described by Rousseau, is in fact a great benefit to their society. A society without this is a stagnant society. Is it preferable to remain stagnant, ignorant but happy? According to the categorical imperative of Kant, it is a crime against oneself.

Extravagance is a kind of eccentricity, related to abundance and wastefulness.

For extravagant text, see also hyperbole.

See also List of notable eccentrics.