 Toroid

A toroid is a ring-shaped surface of revolution obtained by rotating a closed planar profile about an axis in its plane that stays outside the profile. A circular profile gives a torus; a rectangular profile gives a ring with rectangular cross-section. The enclosed solid supplies the core geometry in a toroidal winding, while the mathematical surface is its boundary. The distinction matters when computing a surface area versus a volume.

A toroid is a three-dimensional geometric shape that resembles a doughnut or ring. Mathematically, a toroid can be defined as a surface of revolution generated by rotating a closed curve (usually a circle) around an axis that is coplanar with the curve but does not intersect it.