1. The properties of a circle and how you can identify it.
Circles
The properties of a circle and how you can identify it.

2. Centre point
The centre point is the middle of the circle. The centre point in this picture is the point marked 0.

3. Diameter
The diameter of a circle is a line that goes through the circle and through the centre point.
The algebraic form for the diameter is D=2R
The algebraic form for the diameter is D=2R

4. Circumference
The circumference is the outside of the circle. You measure it using length. You can calculate it using a formula.

5. The radius is a line from the centre point to the circumference
The radius is a line from the centre point to the circumference. The line is always the same length.
Radius
The algebraic form for the radius is D/2
The algebraic form for the radius is D/2