Editing Circumference (section)

{{Short description|Perimeter of a circle or ellipse}}
{{For|the circumference of a graph|Circumference (graph theory)}}
[[File:Circle-withsegments.svg|thumb|{{legend-line|black solid 3px|circumference ''C''}}
{{legend-line|blue solid 2px|diameter ''D''}}
{{legend-line|red solid 2px|radius ''R''}}
{{legend-line|green solid 2px|center or origin ''O''}} Circumference = {{pi}} × diameter = 2{{pi}} × radius.]]
{{General geometry}}

In [[geometry]], the '''circumference''' ({{etymology|la|{{wikt-lang|la|circumferēns}}|carrying around, circling}}) is the [[perimeter]] of a [[circle]] or [[ellipse]]. The circumference is the [[arc length]] of the circle, as if it were opened up and straightened out to a [[line segment]].<ref>{{citation|first1=Jeffrey|last1=Bennett|first2=William|last2=Briggs|title=Using and Understanding Mathematics / A Quantitative Reasoning Approach|edition=3rd|publisher=Addison-Wesley|year=2005|isbn=978-0-321-22773-7|page=580}}</ref> More generally, the perimeter is the [[curve length]] around any closed figure. 
Circumference may also refer to the circle itself, that is, the [[Locus (geometry)|locus]] corresponding to the [[Edge (geometry)|edge]] of a [[Disk (geometry)|disk]]. 
The {{em|{{visible anchor|circumference of a sphere}}}} is the circumference, or length, of any one of its [[great circle]]s.