What can be said about the relationship between triangles and circle

Following are relation between Circle and Triangle:

1. Both circle and triangles are plane figures.

2. One circle is inscribed in a given triangle which is the largest circle that can be inscribed while Many triangle cane be inscribed in a circle. This circle is called incircle.

3. There also only one circle that passes through all vertices of a triangle. That circle is called circumcircle.