| Term | Definition |
| median | a segment whose endpoints are a vertex of a triangle and the midpoint of the side opposite the vertex |
| centroid | the point of concurrency for the medians of a triangle |
| centroid theorem | the centroid of a triangle is located on a median two thirds of the distance from a vertex to the midpoint of the opposite side |
| altitude | a segment from a vertex to the line containing the opposite side and perpendicular to the line containing that side |
| orthocenter | the point of concurrency of the altitudes of a triangle |