A cevian is a line segment in a triangle that connects a vertex to the opposite side. This line can be drawn from any of the three vertices of the triangle, dividing the triangle into two smaller triangles. Cevians can be used in various geometric calculations and proofs, making them an important concept in geometry. One well-known property of cevians is that they can intersect at a single point called the centroid, which is the point where the three medians of the triangle meet. The centroid divides each median into a ratio of 2:1, providing a useful way to find the center of mass of a triangular shape.