Eccentric usually describes people and things that deviate from conventional or accepted usage or behavior, especially in odd or whimsical ways. It is also used technically to mean "deviating from a circular path" and "located elsewhere than at the geometric center."

// He's an endearingly eccentric scientist whose methods are quite inventive.

// The dwarf planet Pluto has an eccentric orbit.

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"The film [Annie Hall] is considered one of the great romantic comedies of all time, with [Diane] Keaton's eccentric, self-deprecating Annie at its heart." — Eva Roytburg, Fortune, 11 Oct. 2025

Eccentric was originally a technical term at home in the fields of geometry and astronomy. It comes from the Medieval Latin adjective ecentricus, meaning "not having the earth at its center," and ultimately has its root in a Greek noun, kéntron, whose various meanings include "stationary point of a pair of compasses" and "midpoint of a circle or sphere." But its figurative use is long-established too: as far back as the 17th century the word has been used to describe people and things that deviate from what is conventional, usual, or accepted.