# What do you call a cylinder with a hole down the center?

Imagine a 3D cylinder, like a can. Now imagine that almost like an axle spot for a wheel, there's a hole shaped in a perfect circle going down the cylinder. That's the shape I have to figure out the name for. Mathematical names are preferred, but any name works!

• There's only 1D in cylinder. Commented Feb 24, 2015 at 21:46
• I think you call it a "pipe". (Well, actually, "cylinder" is the common term, unless it's exceptionally long.) Commented Feb 24, 2015 at 22:24
• So you mean basically like a very tall doughnut? Commented Feb 24, 2015 at 22:37
• Tube. Thick-wall or thin-wall. If cylinder is short enough, the holed variety might be called a washer. Commented Feb 25, 2015 at 0:27
• A man, a worm, and a straw are topolgically equivalent.
– tchrist
Commented Feb 25, 2015 at 4:12

A solid cylinder with an axial hole is still a cylinder. If the length of the cylinder is very much less than the diameter and the bore is small compared to the diameter it is a washer. If the length is much larger than the diameter, and especially if the bore is nearly as large as the cylinder diameter it is a tube.

• I think "washer" is only likely to be properly recognized in mechanical contexts, and may be especially misleading or inappropriate for some others.
– Iszi
Commented Feb 24, 2015 at 23:13
• "washer" is used in mathematical contexts for integration of certain types of functions. Commented Feb 25, 2015 at 3:38
• True: I might say "like a washer" rather than describing it as a washer. Commented Feb 25, 2015 at 5:41
• A cylinder with `length < diameter` is still a cylinder. Commented Feb 25, 2015 at 9:55
• Yes,but if length << diameter it's also a washer. Commented Feb 25, 2015 at 20:26

Cylinder -Wiki

Open Cylinder

A cylinder -with the generating lines perpendicular to the bases, with its ends closed to form two circular surfaces- with a hole perpendicular to its base, is a right circular, open cylinder.
Its function tells us if it's a pipe, washer, bearing, beer can, ect.

Google's 4th picture hit for open cylinder:

• Sorry, but this is mistaken. An open cylinder is a surface, not a 3D solid, and the image is wrong or at the very least, highly misleading. See details in my answer here. Commented Dec 2, 2023 at 10:10

In technical terms, it seems that the three dimensional object would be called an annular cylinder:

A problem in generalized thermoelasticity for an infinitely long annular cylinder

Annulus is certainly a two-dimensional object in geometry describing one cross section of an open cylinder:

NOUN

technical

1 A ring-shaped object, structure, or region.

A barrel is also a common less technical reference for a bored cylinder:

A cylindrical tube forming part of an object such as a gun or a pen:

Tube, pipe and ring also offer less technical descriptions.

International Journal of Engineering Science Volume 26, Issue 3, 1988, Pages 301–306

www.oxforddictionaries.com

en.wikipedia.org

• Annulus appears to be 2D... Commented Feb 24, 2015 at 22:01
• Though mathematically similar, an annulus is considered very flat (like a washer) or even 2D. Much of any depth to it and people wouldn't call it an annulus anymore. I don't have a good single word for what is desired but a 'cylinder with bored/rifled center'. Commented Feb 24, 2015 at 22:01
• As the other comments mention, an annulus is 2-dimensional; this object is an annular cylinder. Commented Feb 25, 2015 at 1:55
• I recall encountering some writing by a non-native speaker that used annulus. That's unheard of in American English and I suggested ring for that particular use. Commented Feb 25, 2015 at 5:39
• @jdlugosz: In technical mathematical writing, annulus is the recognized term for the 2-dimensional shape, partly because ring is used in mathematics for something completely different. Commented Feb 25, 2015 at 6:08

Colloquially, i'd just call it a hollow cylinder.

• Not just colloquially. Whenever this shape appears in physics, it's called a hollow cylinder. Commented Feb 24, 2015 at 23:32
• If I read the phrase "hollow cylinder", I'd be wondering if it had end-caps or not. Commented Feb 25, 2015 at 18:20
• … not to be confused with a foolish Dutchman. Commented Feb 25, 2015 at 22:35
• But wouldn't it be weird to call a cylinder with a 12cm diameter "hollow" if it had only a 1mm axial center-bore?
– TimR
Commented Dec 2, 2023 at 13:16

I've always considered that a Toroid

http://en.wikipedia.org/wiki/Toroid

• "toroid" is a bit too vague. It is like calling a square a quadrilateral. Commented Feb 25, 2015 at 20:59
• You can call it a "rectangular toroid" to specify the shape of its cross section.
– Muqo
Commented Feb 26, 2015 at 15:34
• No, it would be a circular toroid. The premodifier to toroid describes the cross section, not the projected profile. Commented Dec 2, 2023 at 16:51

Stealing from other answers as well.

• Tube (if it's longer than it is wide)
• Tunnel (if it's a tube big enough to crawl or drive through)
• Pipe (if it's long and fixed in place)
• Hose or Conduit (if it bends)
• Ring or Disc or Washer (if it's shorter than it is wide)
• Straw (if you drink through it)
• Bucket (if it has a cover on one end)
• Bottle (if it's a bucket with the open end narrower than the closed end)
• Can or Canister or Capsule (if it has a cover on both ends)
• Duct (if it has junctions)
• Barrel (if you shoot projectiles through it, or it's made of compressed wood planks, or it's a canister big enough to store a person)
• Toroid (if its ends meet)
• Sleeve (if it's designed to snugly surround something)
• Coil or Solenoid (if it's made by tightly winding material around a cylinder)
• Bushing (if it has internal, inverse screw threading)

In the UK Steel Industry it is referred to as a Hollow Bar

In French, it would be called "un manchon". I found the following translations for this word: muff, sleave, bush(ing), socket. I don't know which one is the most appropriate.

• I think within an engineering context, bushing and sleeve are reasonable suggestions. Commented Feb 25, 2015 at 17:07
• Tube
• Ring
• Pipe
• Washer
• Straw
• Hollow cylinder
• Cylindrical shell
• Bored cylinder

Or, perhaps the most technical name for it:

• Long round thing with a hole through it

It's called a tube - a hollow cylinder. E.g.; gun barrels are sometimes called metal tubes; plastic sewer pipes get addressed as tubes; and architects get the privilege to call tunnels tube-shaped structures.

In Mathematics, the shape the OP describes is a cylindrical shell, which is a 3D solid more colloquially called a "tube" or "pipe" or some of the other terms @wberry listed.

The term "cylinder" itself is now quite ambiguous, referring both to a 3D solid in some contexts and the surface area of such a solid in other contexts. Where it refers to a surface area, the surface area includes the areas of the disks at either end. The term open cylinder refers to the surface area of just the sides of the solid, without the end disks. An open cylinder is not a 3D solid.

This is what I remember using in geometry class: "coaxial cylinders". Pipe is correct too. Disclaiming that the hole is not implied there. This question is very close to yours, check it out.

In mathematics, prism is used to describe a 2D object projected along a third axis to form a 3D object. As long as the bores are coaxial and concentric, call it a annular prism. If the third axis is perpendicular to the 2D plane, it is a right annular prism. This will work in any technical context where you want a generalized term for this concept.

However, once you have a specific context or example, annular prism becomes unwieldly, and I'd just call any specific one of these a cylinder.

So if you want to talk about automating FEA grid optimization for these forms, annular prism is the way to go. But when it comes time for the machinist to make one, they make you a cylinder.

Note, toroidal prism is a type of polyhedron - it's an easy mistake to make.

You also want to make sure there aren't any ideas of light refraction attached.

"Free vibration analysis of bi-directional functionally graded annular plates using finite annular prism methods"

When light refraction is the central idea, don't use annular prism - use prism rod (lead with the word prism when talking about light refraction) - https://www.swiftglass.com/portfolios/prism-rods.