# What is the name for a shape that is like a capsule, but with two different radii?

I'm looking for the name of a shape that is like a capsule, but where each circle can have different radii. The shape could be described using two circles (two centers and two radii). Something like this (this is a 2D shape, not a lame attempt at 3D):

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You can just say it is the convex hull of two circles.

• Yeah that's a simpler definition. A name would be cool though, as I'd like to use it as the name of a class in a program and ConvexHullOfTwoCircles is not too catchy. Jul 31, 2010 at 1:29
• What about Pear? Jul 31, 2010 at 2:13
• It looks like a pulley and belt system, so how about PulleyBeltShape? Jul 31, 2010 at 4:45
• I'm accepting this because the shape doesn't seem to have a name and this is a helpful definition. Jul 31, 2010 at 12:56
• @Qiaochu Haha, Pear's not bad but, if you're into fruits, Avocado seems more fit! Jul 31, 2010 at 13:05

Here is an article at Mathworld on Circle-Circle Tangents. Perhaps "CirclesWithTangents"?

(source: wolfram.com)

• Hmm... not too sure for the name, but thanks for that article, it should be helpful with what I intend to do with this shape. Jul 31, 2010 at 12:55
• @Dennis Williamson Circle with Direct tangents Sep 5, 2014 at 23:42

I would suggest the name "Capsuloid". I had the same question but in $3D$. One could define the capsuloid ratio as the quotient of smallest radius $r$ to biggest radius $R$. $r\over{R}$ belongs to $[0,1]$, a value of $1$ corresponding to a true capsule.

• Please use Mathjax Jul 18, 2017 at 13:44
• Oh great I didn't know it was available! Super noob here :) Thanks! Jul 19, 2017 at 13:21

I have 3 ideas from which you may be able use to settle upon a suitable name:

• a conrod or tapered conrod (as in the big-end small-end connecting rod);

• it resembles a pull tab of a zipper; and,

• it also resembles the tab pull of a soda can.