You can call it a "triangular prism" rather than "triangular based prism" ... saying a prism is "triangular" imply that the base is a triangle. There's no other name that I know of. A prism is just a 3d shape, so all you have to say is <type of shape> + prism to get the point across.
Altitude
A Pentagon.
An octagon-based prism.An octagon-based prism.An octagon-based prism.An octagon-based prism.
altitude
It is the height of the prism. There is no need for another name!
A prism cannot be used to name an ordered pair.
Twice the name. A prism with an n-sided base will have 2n vertices.
A twelve-sided prism is called a dodecagonal prism. The prefix "dodeca-" denotes twelve sides, while "gon" refers to a polygon. In geometry, a prism is a polyhedron with two parallel and congruent faces called bases, and its other faces are parallelograms. A dodecagonal prism would have twelve sides, twelve vertices, and twenty-four edges.
a hexagonal prism
Prisms (not prism's) got their (not there) name from the Greek prisma, meaning sawed.
is a prism named according to the shape of its base
The answer depends on where it is that their name is.
Triangular prism
A brick, book, dresser or shelf, a toy chest or a rectangular box.
Divide the number of vertices by 3. Find the name of the polygon with that many sides. The prism has that polygon as a base. For example, a prism with 24 vertices. Divide by 3 so that is 8. An 8 sided polygon is an octagon. The name is an octagon-based prism.
It is simply called a pentagonal prism. That is a prism based on the 2D shape known as a pentagon.