Does surface have thickness?

Hi,

Does surface have thicnkess?

If we use "Extrude boss/base" to create a solid from a sketch, basically we are extrude a 2D sketch area into a 3D solid, which obviously has thickness; however when we extrude a 1D sketch profile into a surface, basic math says that it is a 2D object, so I presume it is without thickness?

More generally, the strict mathematical definition for "surface" mean each surface can be defined by a equation (either explicit or implicit (parametric)) with only two INDEPENDENT variables, so by definition a surface cannot have thickness. In Solidworks, do other types of surfaces aside from extruded type have thickness?

Qi

SolidworksParts And Features