A polygon is a 2-dimensional figure bounded by three or more straight lines. Any one of its sides may be considered a base.
Tetrahedron
pyramid
It is simply called a face.
A hemisphere is one example.
It can be a triangular based pyramid
A pyramid.
A polygon is a 2-dimensional figure bounded by three or more straight lines. Any one of its sides may be considered a base.
A polyhedron is a three-dimensional figure formed by flat surfaces that are bounded by polygons joining along their sides (the faces of the polyhedron).A circle is not a polygon, but we can say that a circle is the limit of a regular polygon with n sides. It means that if n becomes larger and larger, the polygon shape approaches to a circle. A circle is a two dimensional figure as a polygon is, but a three dimensional figure whose base(s) is/are a circle cannot be called a polyhedron.
No. Polyhedra are three-dimensional objects, and the base of any prism, strictly speaking, should be two-dimensional. Any convex polygon (which is two-dimensional) can form the base of a pyramid. A circle, which is technically not a polygon, is the only convex two-dimensional figure that cannot form the base of a pyramid because it forms the base of a cone.
Tetrahedron
Because the base of a cone is round, it is the only three dimensional figure with only one vertex.
pyramid
pyramid or cone
A cylinder is a basic geometric three dimensional figure. The base is a circle. A cylinder can be described as an enclosed tube. It cannot be classified as a polygon since all of the sides are not segments.
It is simply called a face.
A hemisphere is one example.