What does excentric mean?
"Excentric" is a variant spelling of "eccentric," used mainly in older technical and engineering texts. In mechanics, an excentric is something mounted off-centre — typically a disc or wheel fixed to a rotating shaft with its centre deliberately offset from the shaft's axis, so that as it turns it produces a back-and-forth, reciprocating movement. This principle drove valves in steam engines and locomotives, where terms such as "excentric rod" and "excentric strap" appear throughout nineteenth-century manuals. Beyond mechanics, the word carries the same sense as "eccentric" more generally: off-centre, irregular, or deviating from what is usual, including in descriptions of unusual behaviour or character. Today the spelling survives almost exclusively in historical documents, patents, and preserved machinery literature; modern writers use "eccentric" for all senses. Knowing "excentric" is therefore useful chiefly for reading Victorian-era engineering works accurately rather than for contemporary composition.
Not centrally placed; having its axis or centre offset from that of another body or from the centre of rotation; by extension, deviating from the conventional.
"The excentric disc rotated about a point away from its own centre."
Chiefly found in historical or technical contexts; standard modern usage prefers "eccentric".
A disc or wheel mounted on a rotating shaft with its centre offset from the shaft's axis, used to convert rotary into reciprocating motion.
"The valve gear was actuated by an excentric keyed onto the main shaft."
Used primarily in older British mechanical engineering terminology.
Applies to the noun sense referring to mechanical devices.
"Both excentrics were re-machined during the locomotive's overhaul."
Before engineers settled on 'eccentric', they wrote 'excentric' — a spelling that survives today mostly in old machinery manuals and locomotive diagrams.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of excentric
"Excentric" derives from the same source as "eccentric": the Latin "excentricus", from Greek "ekkentros", combining "ek-" (out) and "kentron" (centre). It entered English around the early seventeenth century as an alternative rendering of the Greek prefix, and persisted alongside "eccentric", especially in British technical writing. Its cognates include "centre"/"center", "central", and "centrifugal", all from the Greek "kentron" via Latin.
How excentric is actually used
This form is rare and largely historical or technical; in general writing, 'eccentric' is the standard spelling. The '-ex-' spelling appears most often in older British mechanical and railway literature.
Easily confused with excentric
'Excentric' is a rare, now largely obsolete or technical spelling; the standard modern word for both off-centre placement and unconventional behaviour is 'eccentric'.