Cone....
A shape cannot have only one side because it would not be closed. A shape must have at least three sides to be a closed figure (no "gaps")
the shape has 1 side of symmetry
The only shape with one side is a circle. In geometry, a circle is defined as a shape that consists of all points in a plane that are a fixed distance, called the radius, from a given point, called the center. Since a circle is a curved shape with no angles, it can be said to have only one side, as there are no distinct edges or boundaries that separate it into multiple sides.
It is not possible to have 1 parallel side since it must be parallel to another side. A four sided shape with 1 PAIR of parallel sides is a trapezium (or trapezoid).
A semicircle is one shape fitting this description.
Not sure how you can have only one parallel side. What is it parallel to?
Cone....
A shape cannot have only one side because it would not be closed. A shape must have at least three sides to be a closed figure (no "gaps")
a circle
No shape has only 1 parallel side. A trapezoid is a 4-sided shape, or quadrilateral, with only 2 parallel sides; it does not necessarily have to have 2 right angles. (In the UK a trapezoid is called a trapezium.) In North America, a trapezium is a quadrilateral with 0 (no) parallel sides.
a circle
A semicircle.
If you mean one pair of parallel lines, then you're talking about a trapezoid.
A two dimentional shape with 1 side and 1 vertex.
A vertical line
A sphere