Editing Euler line (section)

===Tetrahedron===
{{Main article|Tetrahedron#Properties analogous to those of a triangle}}

A [[tetrahedron]] is a [[three-dimensional space|three-dimensional]] object bounded by four triangular [[face (geometry)|faces]].  Seven lines associated with a tetrahedron are concurrent at its centroid; its six midplanes intersect at its [[Monge point]]; and there is a circumsphere passing through all of the vertices, whose center is the circumcenter. These points define the "Euler line" of a tetrahedron analogous to that of a triangle. The centroid is the midpoint between its Monge point and circumcenter along this line. The center of the [[twelve-point sphere]] also lies on the Euler line.