Pi ($\pi$) is an important number when we talk about circles. It helps us figure out how big around a circle is and how much space is inside it.

Circumference

The circumference ($C$) of a circle tells us how long the circle is around the edge. We can find it using this formula:

$$C = 2\pi r$$

Here, $r$ is the radius, which is the distance from the center of the circle to the edge.

For example, if a circle has a radius of 3 cm, we calculate the circumference like this:

$$C = 2\pi(3) = 6\pi \approx 18.84 \text{ cm}$$

Area

The area ($A$) of a circle shows us how much space is inside it. We use this formula:

$$A = \pi r^2$$

So, if we use the same radius of 3 cm, the area is calculated like this:

$$A = \pi(3^2) = 9\pi \approx 28.27 \text{ cm}^2$$

In simple terms, $\pi$ helps us connect how far around a circle is (circumference) with how much space is inside it (area). This knowledge is really useful in real life, especially in fields like building design and engineering!