Post Summarization: ● Definition of circle. ● Diameter. ● Radius. ● Circumference or Periphery. ● Arc. ● Chord. ● Segment. ● Sector. ● Quadrant. ● Tangent and Normal. ● Concentric circles. ● Eccentric circles. ● Tutorial videos. Circle (Definition): A plane figure bounded by a curve which formed by a Locus of a Point that rotates on a path so that it is always at a fixed distance from a stationary point (Centre point). Terms Used In Circle: Some terms are frequently used in circles. These are as follows: Diameter: The length of a straight line between two points on the curve and passing through the center point of the circle is called Diameter . It is denoted by ' D ' or ' d ' or ' Φ ' (Phi). Radius: The length of a straight line, between any point on the curve to the centre point is called a Radius . It is half (i.e. D/2) of the diameter. Radius is denoted by ' R ' or ' r '. Circumference Or Periphery: The linear length of the entire curve