Circles are 2D shapes with one side and no corners. The circumference is always the same distance from the centre - the radius. Sectors, segments, arcs and chords are different parts of a circle.
Part of MathsGeometry and measure
A chord is a straight line joining two points on the circumference of a circle.
An arcclosearcThe curve between two points on the circumference of a circle. is a part of the circumference of a circle.
A segment is an area enclosed by a chord and an arc.
A sector is an area enclosed by two radiicloseradiusThe distance from the centre of a circle to its circumference. The plural of radius is radii. and an arc.
A tangent is a straight line which touches the edge of a circle.