# Thread: Can anyone tell me the real names of these 3D shapes?

1. I know cylinder, cone and cube, but can't think of the names for the last two. I know this is a very basic question that I should know...but I am blanking.

2. The last two are prisms, a rectangular prism and a right triangular prism.

3. Second last one is precisely known as cuboid and the last one is a triangular prism (as MarkFL said).

4. Originally Posted by Prakhar
Second last one is precisely known as cuboid and the last one is a triangular prism (as MarkFL said).
I don't think there's anything precise with the term "cuboid" as it simply means "cube-like". "Rectangular Prism" is much more specific, as being a 3D shape with all identical rectangular cross-sections...

5. Originally Posted by Prove It
I don't think there's anything precise with the term "cuboid" as it simply means "cube-like". "Rectangular Prism" is much more specific, as being a 3D shape with all identical rectangular cross-sections...
If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal.

6. Originally Posted by Prakhar
If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal.
From :
In geometry, a cuboid is a convex polyhedron bounded by six quadrilateral faces, whose polyhedral graph is the same as that of a cube. While mathematical literature refers to any such polyhedron as a cuboid,[1] other sources use "cuboid" to refer to a shape of this type in which each of the faces is a rectangle (and so each pair of adjacent faces meets in a right angle); this more restrictive type of cuboid is also known as a rectangular cuboid, right cuboid, rectangular box, rectangular hexahedron, right rectangular prism, or rectangular parallelepiped.[2]

So for starters "cuboid" is somewhat ambiguous, and more specifically mathematical literature refers to it without requiring right angles or square faces, while cube and right rectangular prism are well-defined with square respectively rectangular faces.

7. Originally Posted by Prakhar
If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal.
Ancient mathematicians also believed that all numbers were rational and killed anyone who could prove otherwise. Yes, why not use their logic???

8. Originally Posted by I like Serena
From :
In geometry, a cuboid is a convex polyhedron bounded by six quadrilateral faces, whose polyhedral graph is the same as that of a cube. While mathematical literature refers to any such polyhedron as a cuboid,[1] other sources use "cuboid" to refer to a shape of this type in which each of the faces is a rectangle (and so each pair of adjacent faces meets in a right angle); this more restrictive type of cuboid is also known as a rectangular cuboid, right cuboid, rectangular box, rectangular hexahedron, right rectangular prism, or rectangular parallelepiped.[2]

So for starters "cuboid" is somewhat ambiguous, and more specifically mathematical literature refers to it without requiring right angles or square faces, while cube and right rectangular prism are well-defined with square respectively rectangular faces.
Does the diagram posted by OP specify right angles or square faces?
Also, how would you define a cuboid?

9. Originally Posted by Prove It
Ancient mathematicians also believed that all numbers were rational and killed anyone who could prove otherwise. Yes, why not use their logic???
They believed! They did not decide that. However, the name cuboid was "assigned".

10. Originally Posted by Prakhar
Does the diagram posted by OP specify right angles or square faces?
Also, how would you define a cuboid?
Examples of cuboids... I think they look different from what is shown in the OP...