# Circles - Circumference of a circle Part 2

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The circumference is the length of the edge around a circle.

For any circle, the circumference is:

3.141592... x the diameter.

Or in symbols: C = (3.141592...)d.

This is true for all circles and so 3.1414592... is therefore a special, unique number, and we represent it with the Greek letter  π.( The symbol π is called 'pi' in English and is pronounced 'pie').

So we can write the formula for the circumference of a circle as: C = πd.

However, the diameter is equal to 2 x radius, (2r), so we can also wrtie this formula as:

C