Are yams and sweet potatoes the same?
helicoid hel·i·coid (hěl'ĭ-koid', hē'lĭ-)
Arranged in or having the general shape of a flattened coil or spiral.
Adjective Arranged in or having the approximate shape of a flattened coil or spiral curve.
Noun A surface in the form of a coil or screw. A helicoid is generated mathematically by rotating a plane or twisted curve about an axis at a fixed rate and simultaneously translating it in the direction of the line of axis, also at a fixed rate.