### Circles – What You Need to Know for GCSE Maths

Firstly, you need to be aware of some key terminology related to circles. The diagrams below show the things you need to be able to name and recognise. Start with the circumference, which is the distance all the way around the circle. Next remember the radius (the distance from the centre to the circumference of the circle) and the diameter (the distance through the centre from one side of the circumference to the other). The diameter is the distance through the centre from one side of the circumference to the other.

#### Other key terms for circles

The two diagrams below show you the other key things you need to be able to name and recognise:

• Chord – a line from one point on the circumference to another.
• Minor Segment – smaller part of the circle created by a chord.
• Major Segment – larger part of the circle created by a chord.
• Tangent – a straight line outside the circle, which just touches the circumference.
• Sector – a part of the circle created by two radii (it looks a bit like a pizza slice).