# Name for a geometric shape? **URL:** \ **Category:** Factual Questions\ **Created:** [November 29, 2024, 4:32pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939 "2024-11-29T16:32:19Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 29, 2024, 4:32pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/1 "2024-11-29T16:32:19Z")
Is there a name for this shape: Basically a square or rectangle with curved sides. Two of those on opposite sides curve inward and the other two curve outward. If they have the same curvature and length, they’ll tile the plane, but I expect the name would apply even if they didn’t. I’d link to a picture, but I need the name to google it. \>\>Rectangle with curved sides\<\< does not bring up an image. ---
**Author:** ![Zoobi](https://avatars.discourse-cdn.com/v4/letter/z/13edae/32.png) [@Zoobi](https://boards.straightdope.com/u/Zoobi)\ **Post date:** [November 29, 2024, 5:03pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/2 "2024-11-29T17:03:03Z")
I’ve seen it called “apple core” if I’m understanding you correctly. ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [November 29, 2024, 5:04pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/3 "2024-11-29T17:04:35Z")
Do you mean [astroids](https://en.wikipedia.org/wiki/Astroid)? ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 29, 2024, 5:06pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/4 "2024-11-29T17:06:51Z")
Nope, not astroid. That has all sides concave. I’m looking for a shape with two convex and two concave. “Apple core” might be it. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [November 29, 2024, 5:28pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/5 "2024-11-29T17:28:18Z")
I think it probably is. I googled “flat tiles apple core shape,” which led me to “apple core template,” for which the images primarily lead to quilting patterns. ETA: I also saw mention of “axe blade.” Doesn’t seem to be as common under that search term. ---
**Author:** ![Baal\_Houtham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/baal_houtham/32/13604_2.png) [@Baal\_Houtham](https://boards.straightdope.com/u/Baal_Houtham)\ **Post date:** [November 29, 2024, 5:55pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/6 "2024-11-29T17:55:17Z")
> [@kaylasdad99](#): > > ETA: I also saw mention of “axe blade.” Doesn’t seem to be as common under that search term. Yeah, most results I found were from quilting sites. I didn’t see “axe blade” but saw ax head and double bit axe. The axe terms obviously refer to a double-headed axe. ---
**Author:** ![FrenchDunadan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frenchdunadan/32/5449_2.png) [@FrenchDunadan](https://boards.straightdope.com/u/FrenchDunadan)\ **Post date:** [November 29, 2024, 6:33pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/7 "2024-11-29T18:33:52Z")
like this ones? > **[Axe Head Border in Black and Burnt Red Stone](https://deferranti.com/index.php/products/view/5540c30fc2fa7)** > > Let the colours of Pompei coupled with black limestone enhance your interior setting and mood called axe head tiles. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [November 29, 2024, 6:55pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/8 "2024-11-29T18:55:01Z")
Here’s an image of the apple core tiling, which is indeed the same as the ax head. > **[Westalee Design Apple Core Template 3pc Set | Sew Steady](https://www.sewsteady.com/product/westalee-design-apple-core-template-3pc-set/)** > > Create beautiful continuous background fill designs and much more with this 3pc set. Template sizes ranging from 1” - 3”. Designed by Leonie West of Westalee Design. Scientific American just ran an article on newly-found soft three-d tilings with no corners. > **[Newly Discovered Shape Is a Tessellation Revelation](https://www.scientificamerican.com/article/mathematicians-discover-a-new-kind-of-shape-thats-all-over-nature/)** > > Mathematicians have found a new kind of shape with connections to nature and art ---
**Author:** ![EinsteinsHund](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/einsteinshund/32/8400_2.png) [@EinsteinsHund](https://boards.straightdope.com/u/EinsteinsHund)\ **Post date:** [November 29, 2024, 9:03pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/9 "2024-11-29T21:03:08Z")
The oldest example for this shape I can think of is the Minoan double-axe, but it may be older. [![](https://www.greekartworks.com/wp-content/uploads/2024/07/minoan-double-axe-labrys-knossos-palace-3.webp) ](https://www.greekartworks.com/wp-content/uploads/2024/07/minoan-double-axe-labrys-knossos-palace-3.webp) ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [November 29, 2024, 9:17pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/10 "2024-11-29T21:17:24Z")
> [@EinsteinsHund](#): > > The oldest example for this shape I can think of is the Minoan double-axe Called a labrys as in labryrinth. It was the symbol of the Minoan state. ---
**Author:** ![EinsteinsHund](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/einsteinshund/32/8400_2.png) [@EinsteinsHund](https://boards.straightdope.com/u/EinsteinsHund)\ **Post date:** [November 29, 2024, 9:32pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/11 "2024-11-29T21:32:38Z")
Yes, I know, I visited Crete and the Archaeological Museum of Iraklion twice, the palaces of Knossos and Phaistos once. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 30, 2024, 3:30am UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/12 "2024-11-30T03:30:38Z")
I always thought it odd, when I read of the Lune of Hippocrates as a youth, because it was considered so revolutionary when it was discovered, that it was possible to determine the area of a shape none of whose edges were straight lines. But of course, there are a whole set of shapes like the OP is describing (apple cores or axe heads or whatever), plus another whole set where the convex sides (and hence also the concave sides) are adjacent, which also meet that description, but whose areas are trivial. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 30, 2024, 1:09pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/13 "2024-11-30T13:09:30Z")
I was thinking “cookie with two bites out of it…” ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [November 30, 2024, 2:47pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/14 "2024-11-30T14:47:37Z")
I think the lune was considered remarkable because although it was made from curved shapes, its area was equal to the area of a (particular) triangle ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 30, 2024, 3:08pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/15 "2024-11-30T15:08:01Z")
Right, but so is this shape. The ancients knew how to construct a square with the same area as any triangle, or vice-versa. In fact, the problem was usually posed as “given this shape, find a square with the same area”, and the only reason you stop with the triangle with the lune is because everyone knows how to do the last steps. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [November 30, 2024, 3:20pm UTC](https://boards.straightdope.com/t/name-for-a-geometric-shape/1010939/16 "2024-11-30T15:20:42Z")
Ah, good point. I suppose the lune was just the first one thought of, so it stood out (and it’s an elegant proof).