A line segment joining a vertex of a tetrahedron with the centroid of the opposite face is called a median. [br]A line segment joining the midpoints of two opposite edges is called a bimedian of the tetrahedron. [br]Hence there are four medians and three bimedians in a tetrahedron. [br]These seven line segments are all concurrent at a point called the [b]centroid[/b] of the tetrahedron.