there are 4 edges
it has 0 curved edges
there are no curved edges on any triangle.
There are no curved edges on a triangular pyramid.
There are no curved edges, but it does stack.
A 3 dimensional pentagon has 15 edges
A Pentagon Pyramid has six edges!
A pentagon has 5 edges and 5 vertices
In 3 dimensions, at least, a cube has no curved edges.
A pentagon has five sides.
There is one curved side and two curved edges (the rims along the top and bottom).