Maths Dictionary · JSS 1, SS 2
Diameter
Simple meaning
A straight line across a circle through its centre. It is twice the radius.
Example
A circle with radius 5 cm has diameter 10 cm.
See it
From the Perimeter of Plane Shapes lesson. Try moving things around.
P = 2 × (5 + 3) = 16 cm
Walk round the edge: 16 one-centimetre steps. (Area would be 15 cm².) Drag the blue corner.
Length5 cm
Height3 cm