What does concentricity mean?
Concentricity is the quality of sharing a common centre. When two or more circles, rings, spheres, or cylinders are arranged so that they have exactly the same central point, they are said to be concentric, and concentricity describes this condition. The word appears most often in geometry and in engineering and manufacturing, where it takes on a practical importance: a drilled hole must be truly centred within its housing, and a rotating shaft must run true relative to its bearings. In these contexts concentricity is frequently treated as a measurable quantity — a tolerance to be specified on drawings and verified with instruments such as dial indicators or coordinate measuring machines — and poor concentricity can cause vibration, premature wear, and mechanical failure. Beyond the workshop, the term is applied loosely to anything arranged in rings around a shared middle, such as tree rings or ripples spreading on water. Precise and technical rather than literary, it conveys exactness of alignment.
nounThe quality or state of having a common centre, as of two or more circles, spheres, or cylinders that share the same central point. In engineering and metrology, it also denotes the degree to which the axes of different features of a part coincide.
- The geometric property of two or more circles, spheres, or cylinders sharing the same centre.
- In engineering metrology, the measured deviation between the axes or centres of two nominally coaxial features of a manufactured part.
"The machinist checked the concentricity of the bore with the outer diameter using a dial indicator."
"The tree's growth rings display near-perfect concentricity around the trunk's centre."
"The bearing was rejected because its concentricity fell outside the specified tolerance."
Rarely pluralised except when referring to multiple measured instances or features, e.g. in inspection reports.
"The report listed the concentricities of all five bores."
A shaft can be perfectly round and still fail inspection — because what matters is not its shape but its concentricity, how exactly its centre matches its neighbour's.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of concentricity
Concentricity derives from the adjective 'concentric', which English adopted in the late fourteenth century from Old French 'concentrique' and medieval Latin 'concentricus'. The Latin combines 'con-' ('together') with 'centrum' ('centre'), a word Greek in origin. The noun 'concentricity' was formed later by adding the Latinate suffix '-ity' to denote the state or quality of being concentric. It shares this root with words such as 'centre'/'center', 'central', and 'eccentric' ('off-centre'), which serves as a natural antonym.
Related word forms
How concentricity is actually used
Concentricity is a technical term used chiefly in geometry, engineering, and manufacturing. In GD&T (geometric dimensioning and tolerancing) it has a precise, standardised meaning relating to the coincidence of median points, though in everyday technical speech it is often used more loosely to mean simple coaxial alignment. It carries no emotional connotation and is neutral in register — formal but familiar within technical fields.
Easily confused with concentricity
Concentration refers to the amount of a substance in a mixture or the act of focusing attention, while concentricity refers strictly to sharing a common centre.