Trihedron
/traɪˈhɪdrən/
Definition 1 of 1
Pro Tip 1/3Geometry Term
Trihedron is commonly used in geometry and technical fields to describe a three-faced shape. 
In my geometry class, we learned how to calculate the angles of a trihedron.
Pro Tip 2/3Not Polyhedron
A trihedron has only three surfaces, unlike a polyhedron which has many. 
A cube is not a trihedron; it's a polyhedron because it has six faces.
Pro Tip 3/33D Understanding
Understanding 'trihedron' requires visualization of three-dimensional space, as it's a 3D shape. 
Visualize a corner of a box; it's a trihedron where the faces meet.