In geometry, the only shape that has one surface is a plane.
a sphere
Circle
A hemisphere
hemisphere
A shape with one corner is a triangle. Yes, I know, technically it has three sides, but it only has one corner. So, there you have it, a triangle is the shape you're looking for.
a sphere
Both. ANY 2-dimensional shape ... that is, a shape drawn in a plane, or on a piece of paper ... has only one surface.
a sphere
Sphere
The shape with just one surface is.... a sphere.
A sphere is a three-dimensional shape with one surface. Or: An irregular blob, an ellipsoid, a torus, plus other shapes. The most interesting 3D object with only one side is of course the Moebus strip.
A trapezium is a plane shape and so has only one surface.
A sphere
sphere
A 2D shape is flat and only has a surface area whereas a 3D shape is an object that has surface area and volume.
a cone.
A sphere