# what is a circle in math?

what is a circle in math? Define its parts in detail.  A circle is a locus of points whose distance is constant from some fixed point O. That fixed point is called the center of the circle and the fixed distance is called the radius of the circle. The locus of points is called the circumference of circle. Here OA is called the radius of the circle. All radii of a circle are fixed in length so mOA=mOB.

## What are the basic terminologies of a circle?

### Circumference:

The circumference of a circle has value equal to 2πr where π is the ratio of circumference and diameter (d=2r) of the circle.

### Arc of a circle:

Any portion of circumference of a circle is known as the arc. AEB in the following figure shows the arc. ### Chord of a circle

Any line segment whose end points lie at the boundary of the circle is called chord and any chord passing through the circle is called the diameter of the circle. So a diameter bisects the circle. ### What is the segment of a circle?

A segment of a circle is the portion that is composed of an arc and the chord. The following figure shows how a chord and an arc divides a circle into its major segment and minor segment. Here AMB is the major segment and ASB is the minor segment. ### Sector of the circle

Sector of a circle is composed of two radii and the arc of the circle. Any two radii divides the circle into two sectors: major sector (pink shaded) and minor sector (shaded orange) as shown in the figure below. ### What is the area of a circle?

The area of a circle has the formula of π(r^2).