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