What do you mean by Circles and its properties?

Understand Circles and its properties. Click on the link to Watch the VIDEO explanation: 
Watch Video

Circle
Let us study about a circle and its properties.
The locus of a point moving on a plane such that it is always at a constant distance from the fixed point is called a circle.
The fixed point is called the centre of the circle.
In the fig. O is the centre of the circle.
The line segment joining the centre and any point on the circle is called the radius of the circle.
In the fig. OA represents the radius of the circle.
The length of the closed curved line which makes the circle is called the circumference or perimeter of  a circle.
The line segment joining any two points on the circle is called a chord of the circle.
In the fig. PQ is a chord.
The chord that passes through the centre of the circle is called the diameter of the circle.
CD represents the diameter of the circle.
An arc is a part of a circle. XY is an arc of the circle.