## ::Centre (geometry)

### ::concepts

Centre::triangle    Point::''f''    Polygon::circle    Points::''a''    ''b''::''c''    Geometry::three

{{ safesubst:#invoke:Unsubst||\$N=More footnotes |date=__DATE__ |\$B= {{#invoke:Message box|ambox}} }}

Circle illustration with circumference (C) in black, diameter (D) in cyan, radius (R) in red, and centre or origin (O) in magenta.

In geometry, a centre (or center) (from Greek κέντρον) <ref>http://en.wiktionary.org/wiki/center</ref> of an object is a point in some sense in the middle of the object. According to the specific definition of center taken into consideration, an object might have no center. If geometry is regarded as the study of isometry groups then a centre is a fixed point of all the isometries which move the object onto itself.

Centre (geometry) sections
Intro  Circles, spheres, and segments  Symmetric objects  Tangential polygons and cyclic polygons  General polygons  See also  References

 PREVIOUS: Intro NEXT: Circles, spheres, and segments << >>