Parts of a Circle

What is this line called?

• radius

• diameter

• chord

• sector

Answer explanation

The Radius goes from the centre of the circle to the edge

What is this line called?

• diameter

• segment

• tangent

• chord

Answer explanation

The Chord of a circle is a straight line that connects two points on the circumference of a circle

What is this type of circle called?

• diameter

• segment

• sector

• semi-circle

Answer explanation

A semi-circle is half a circle. The straight line in the semi-circle is the diameter.

What is the shaded area called?

• segement

• sector

• semi-circle

• chord

Answer explanation

A segment of a circle is a region that is bound by an arc and a chord of the circle. The major segment has the largest area, and the minor segment has the smallest area. Generally, you will be asked about the minor segment.

What is the dark line called? (it's around part of the edge only)

• circumference

• chord

• arc

• sector

Answer explanation

An arc of a circle is a portion of the circumference of a circle.

What is this shaded area called?

• radius

• sector

• segment

• semi-circle

Answer explanation

A sector of a circle is a part of the circle that is enclosed by two radii (plural for radius) and an arc

What is the edge of a circle called?

• radius

• diameter

• circumference

• tangent

Answer explanation

The edge of a circle is called a circumference. You can work it out by using the following formula:

C = π x d

C = 2 x π x r

What is this line called that runs through the circle?

• chord

• radius

• diameter

• tangent

Answer explanation

The diameter of a circle is a line that passes through the centre of a circle and has two endpoints at the circumference. It is twice the length of the radius of a circle (i.e. Diameter = 2 x Radius)

What is this line called?

• radius

• tangent

• diameter

• chord

Answer explanation

A tangent of a circle is a straight line that touches the circumference of the circle at only one point.

Fun Fact: The angle between a tangent and radius is always 90 degrees!

What letter is often used to mark the centre of a circle?

• C

• D

• R

• O

Answer explanation

The centre of the circle is often marked as O, as it stands for Origin. Although O is the most common letter, any letter can in fact be used!