1. Circumference Around the circle

2. Arc Part of the circumference

3. Semicircle Half of a full circle

4. Centre The point inside the circle which is equal distant from all points on the circle (equidistant).

5. Radius An interval drawn from the centre of the circle to the circumference

6. Diameter An interval passing the centre, which divides the circle in half. (diameter = 2 x radius)

7. Sector An area cut off by two radii

8. Chord An interval joining two points on the circumference, but not passing through the centre

9. Tangent A line on the exterior of the circle that touches the circumference at one point

10. Minor segment The smaller of the two regions inside a circle bounded by the circle and a chord

11. Major segment The larger of the two regions inside a circle bounded by the circle and a chord

12. ObjectCircumferenceDiameterCircumference Diameter