A circumcircle is a circle that passes through all the vertices of a polygon, particularly a triangle. The center of this circle is called the circumcenter, which is the point where the perpendicular bisectors of the triangle's sides intersect. The radius of the circumcircle is known as the circumradius. In a triangle, the circumcircle can be constructed by drawing the perpendicular bisectors of each side. The circumcircle is significant in geometry as it helps in various calculations and theorems, such as those related to Euclidean geometry and triangle properties.