A triangle.
A sphere
It has 5 corners if it is a 3D shape like a piramid but if it is 2D it is 3
triangle
equilateral triangle
the vertices are the corners to the shape, so you count the corners to whatever shape.
A better name for "corners" would be angles, but the shape's name would be a hexagon
Triangle
A triangle.
A decagon.
That's impossible, because if a shape has sides, then it means it has corners, and vice versa.
a triangle
it would have to be a triangle
A sphere
It has 5 corners if it is a 3D shape like a piramid but if it is 2D it is 3
triangle
equilateral triangle