Circles, disc and annulus

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English: A circle is the set of all points in a plane at a fixed distance, called the radius, from a fixed point, the centre.
For geometry of circle (conic section), see Category:Circle geometry or Circle (Geometry).


English: This shape, the interior of a circle, is called a disc.


English: These are circles proper or, if not to neglect the line thickness, these are rings.