What is defined as the lines of intersection created from three mutually perpendicular planes?

The lines of intersection created from three mutually perpendicular planes are best defined as a coordinate system. In a three-dimensional coordinate system, the three mutually perpendicular planes typically represent the x, y, and z axes. Each axis intersects at a point called the origin, forming a three-dimensional space where positions can be defined.

In contrast to the correct answer, principal axes relate more to the orientation of an object in its respective coordinate system, usually pertaining to the object's own geometry rather than defining the system itself. Reference planes are flat surfaces used as a basis for measurement and do not necessarily imply the intersection of three planes. Orthographic projections refer to a method of representing three-dimensional objects in two dimensions, which does not directly concern the intersection of planes. Therefore, the definition of lines of intersection from three mutually perpendicular planes aligns accurately with the concept of a coordinate system.