Chapter 14 aims to introduce circles, their parts and also concentrates on arcs and chords. Circles play an important role in our daily life. In geometry, circles are defined as closed and two-dimensional curved shapes with no edges or corners. Circles have their notations like diameter, radius, and centre. A centre point in a circle from which all the distances to the points on the circle are the same as the centre of the circle. The circle can also be defined in terms of points, a set of points whose distance from the centre point is the same.
Chapter 14 further sheds light on the different components of a circle, namely, a line segment passing through the centre point and having its endpoints on the circle, known as the circle's diameter. The distance of all the points in the circle from the centre is defined as the circle's radius. It is not necessary that all line segments whose endpoints lie on the circle pass through the centre. The lines touching the circle and not passing through the centre are termed as the chords of the circle, and the diameter is considered the longest chord of the circle.
Circles can be classified into semicircles and quadrants with respect to the angles. If the circle is formed with an angle of 180°, it is known as a semicircle and circles formed with 90° are known as quadrants. Circles of various sizes can be drawn with the help of a radius. The number of diameters of a circle is infinite, and it is concurrent. Both the radius and the diameter are related to each other. The diameter can also be defined as twice the radius.