Theory:

A circle is one of the geometrical shapes which has no corners or edges.

Parts of the circle:

Circumference: The distance once around the circle.

Circular arc: A part of the circumference of a circle $\left(\stackrel{⌢}{\mathit{AB}}\right)$.

Sector: The plane surface that is enclosed between two radii ($$r$$) and the circular arc of a circle $\left(\stackrel{⌢}{\mathit{AB}}\right)$.

Chord: A line segment joins any two-point $$A$$ and $$B$$.

Diameter: A chord $$A$$ and $$B$$ passing through the centre of a circle $$O$$. It also knowns as the longest chord.

Radius: A distance from the centre $$O$$ to the circumference.

Segment: A chord divide the circle into two parts. Each part is termed as segments. In this, the smaller arc is known as a minor segment, and the larger arc is known as a major segment.

Concentric circles: A circle has the same centre but different radii.