Area of any region is the space occupied by the figure on a two dimensional plane surface. We are familiar with the area of a square, rectangle which are obtained by multiplying the length by the width. Circle is a closed figure where a point moves such that it has constant distance from the fixed point. The fixed point is called the center of the circle and the constant distance is called the radius of the circle. We have different terms in circle called, diameter, chord, sector, segment and circumference of a circle. In this section let us discuss with the area of a circle and a semicircle.

Diameter and Radius of a circle: Diameter of a circle is the line segment ( chord ) joining any two points on the circumference of the circle, which passes through the center.
Radius of a circle is the line segment joining the center of a circle to any point on the circumference of the circle.
The following diagram describes the above terms.

Area of a circle is calculated using the formula $\pi$ $r^{2}$
Area of a Circle
where ' r ' is the radius of the circle and $\pi$ an irrational constant = 3.141592653589793238462643383279.
So approximately we take $\pi$ = 3.14 correct to 2 decimal places.

Surface Areas: Surface areas are calculated for three dimensional solid figures like, cube, cuboid, sphere, cylinder, cone etc. Since the circle is a two dimensional figure which is drawn on a plane surface, the surface area of a circle is the same as the area of the circle.