Parts of a Circumference with Diagrams

A circumference is defined as a two-dimensional figure that has a completely round shape. Circles are characterized by having all their points with the same distance from a fixed point. The fixed point is called the center and the distance from the center to the circumference is called the radius. The most important parts of the circle are the center, the radius, the diameter, the chord, the tangent, the secant, and others.

Here, we will learn more details of the parts of the circumference. We will use illustrations to improve our understanding of the concepts.

elements of a circle

Relevant for

Learning about the important parts of a circumference.

See parts

elements of a circle

Relevant for

Learning about the important parts of a circumference.

See parts

Most important parts of a circumference

The main elements of a circumference are:

  • Center
  • Radius
  • Arc
  • Chord
  • Diameter
  • Tangent
  • Secant
elements of a circle


The center is defined as the fixed point that is located inside the circumference. This point is equidistant from any point on the circumference.


The radius of a circle is the constant distance from the center to any point on the circle. The radius is generally represented by the letter r.


The arc is defined as a portion of the circumference. The arc is bounded by two points on the circumference. An angle is used to measure the arc.


The chord is a line segment that is located on the inside of the circumference and that joins a pair of points on the circumference.


A diameter is a line segment that joins two points on the circumference and passes through the center. Diameter is also defined as a chord that passes through the center. The length of the diameter is exactly twice the length of the radius.


The tangent is a straight line that passes through the outside of the circumference and touches it at a single point.


The secant is a straight line that passes through the inner part of the circumference and is touched by two different points.

Additional parts of a circumference

In addition to the most important parts, we also have the following parts in a circumference:

  • Semicircumference
  • Central angle
  • Inscribed angle

Semi circumference

The semi circumference is defined as an arc that is equal to the exact half of the circumference. The semi circumference is limited by the two ends of the diameter.

diagram of semicircumference

Central angle

At a central angle of the circumference, two radii form its sides.

diagram of central angle in a circle

Inscribed angle

At an inscribed angle on the circumference, the vertex is located at a point on the circumference. Also, the sides are formed by two chords of the circumference.

diagram of an inscribed angle

See also

Interested in learning more about circles and circumferences? Take a look at these pages:

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