Talk:regular polygon

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RFD discussion: February–March 2019[edit]

The following information passed a request for deletion (permalink).

This discussion is no longer live and is left here as an archive. Please do not modify this conversation, but feel free to discuss its conclusions.

SOP. Per utramque cavernam 13:36, 3 February 2019 (UTC)[reply]

  • Keep. The use of "regular" here is different from the normal sense of regularity (e.g. a "regular guy"). bd2412 T 15:13, 4 February 2019 (UTC)[reply]
    The regular sense of “regular” is ”following a rule”. So is a “regular guy” someone who follows a rule? Then Benedict monks are regular guys: they follow the Rule of St. Benedict. But I guess “regular guy” means something else; the use of “regular” here is different from the normal sense of regularity. So by the above argument we should have an entry regular guy.  --Lambiam 15:31, 4 February 2019 (UTC)[reply]
    The use of "regular" and "irregular" with respect to polygons are unique to those shapes. Would you call a six-sided shape with five straight sides and one curved side an "irregular polygon"? No, it wouldn't be a polygon at all. bd2412 T 19:02, 4 February 2019 (UTC)[reply]
    Sorry, I cannot follow the argument (apart from the incorrect statement about uniqueness; the concept also applies to polyhedra and in fact also higher-dimensional polytopes). Suppose someone proposes to delete happy customer (“a customer that is satisfied with the service offered”) because it is SOP. Someone argues that it should be kept because this is not the “normal” meaning of happy, although it is one of its listed senses. In response to criticism of that argument (specifically the notion of the “normal” meaning), they now ask: “Would you call a shoplifter that walks out with the goods without being detected a ‘disenchanted customer’? No, they wouldn’t be a customer at all.” Indeed, they wouldn’t, but what has that to do with anything?  --Lambiam 20:08, 4 February 2019 (UTC)[reply]
    A shoplifter could be a disenchanted customer. A shape that is a polygon but for the irregularity of having one non-straight side can't be a polygon. A shape that would be a "regular polygon" but for that difference is therefore neither a regular nor an irregular polygon. bd2412 T 20:26, 4 February 2019 (UTC)[reply]
    I still don’t see the relevance of not calling something a polygon that is not a polygon to the question whether the term “regular polygon” is SoP.  --Lambiam 00:50, 5 February 2019 (UTC)[reply]
    One could easily think that a "regular" polygon means a "typical" polygon, like any triangle, or any five or six-sided figure that doesn't have some crazy indentation. In fact, it is limited to one that is "both equiangular and equilateral". However, the theoretically interchangeable phrases "equiangular and equilateral polygon" and "equiangular equilateral polygon" get one ten-thousandth as many Google Books hits as "regular polygon". I would suggest that a meaning of the word "regular" that only applies when specifically used in combination with a handful of other words, and disproportionately found in only one of those combinations, is idiomatic. Otherwise, we might as well get rid of stop sign and police car, and have entries at "stop" and "police", respectively, reading "when used with sign..." and "when used with car..." bd2412 T 05:31, 5 February 2019 (UTC)[reply]
    I think stop sign and police car are a different thing, but I agree to some extent with you when you say that when a word is found (almost) exclusively in a combination, that combination might be said to be idiomatic. I don't know what the best treatment is for those cases. Per utramque cavernam 18:16, 5 February 2019 (UTC) [reply]
    @BD2412, In no way is this the same. A polygon can be regular, a sign cannot be stop and a car cannot be police. Those are fixed set terms. The note at regular does not say "when used with 'polygon'", it says "of a polygon", i.e. it can describe any kind of polygon. An octagon can be regular or otherwise, you can have regular dodecahedrons, etc etc. "Stop sign" is a set phrase outside of which there is no other use of this sense of "stop". Ƿidsiþ 14:43, 6 February 2019 (UTC)[reply]
    Answered below. bd2412 T 21:47, 6 February 2019 (UTC)[reply]

Keep by all means. An illustration would be useful however. DonnanZ (talk) 15:36, 4 February 2019 (UTC)[reply]

What part of WT:CFI is "all means" referring to? Per utramque cavernam 18:58, 4 February 2019 (UTC)[reply]
By all means is a figure of speech. bd2412 T 19:03, 4 February 2019 (UTC)[reply]
I know, I was jesting. Per utramque cavernam 19:05, 4 February 2019 (UTC)[reply]
Keep - The word regular has 15 different meanings. SemperBlotto (talk) 06:10, 5 February 2019 (UTC)[reply]
Keep - per SemperBlotto. John Cross (talk) 07:56, 5 February 2019 (UTC)[reply]
  • Delete. That's…just what "regular" means in geometry, as it says if you look up regular. So what if "regular" has lots of meanings? You might as well say that regular guy should have an entry in case people think it means "guy who is equilateral and equiangular". Ƿidsiþ 13:07, 5 February 2019 (UTC)[reply]
It does seem redundant to have both this and a sense for this at regular. - -sche (discuss) 17:44, 5 February 2019 (UTC)[reply]
Yes, but if we added a sense at "stop" for a sign saying: "(traffic, of a sign) instructing traffic to cease movement," that would make it seem redundant to have stop sign, although it seems obvious that we should have an entry for it. bd2412 T 21:34, 5 February 2019 (UTC)[reply]
Seriously? That is not at all the same thing. "Stop sign" is the only use of this kind of "stop", whereas lots of things can be geometrically regular. It was not even the earliest use of the word (that was "regular bodies"). Nothing about this indicates a set phrase. Ƿidsiþ 07:38, 6 February 2019 (UTC)[reply]
No it isn't. There is also stop light, and either could be called a "stop signal". bd2412 T 19:50, 6 February 2019 (UTC)[reply]
Nnnnn…I still don't think it's the same, I'm afraid. Noun-noun collocations are always unpredictable because the qualifier can't be used predicatively. It's completely standard to say that a given polygon is regular (or otherwise) – this does not "break" the term in the way that you would expect for a set idiom. Is the polygon regular? Yes, the polygon is regular. It's a regular polygon. You say that the last one is a set term but the other sentences aren't, it doesn't make sense to me. It can also be split with other qualifiers; you could talk about a "regular thirteen-sided polygon". And "regular" can be, and is, applied to any number of different polygons; so in what way, exactly, is it a set phrase if the adjective can be applied in the same way to numerous different nouns, can also be used predicatively, and can be interrupted by further qualifiers? Ƿidsiþ 07:52, 7 February 2019 (UTC)[reply]
So, delete as redundant to the polygon-related sense of regular which is also widely used with other words. - -sche (discuss) 18:16, 7 February 2019 (UTC)[reply]
If we keep regular polygon, should we not logically also have entries for regular quadrilateral, regular pentagon, regular hexagon, regular heptagon etc.? In this case I think the common meaning is better explained at regular, where, as has been mentioned, there is a specific sense labelled "geometry, of a polygon", so it is easy to find. Mihia (talk) 22:04, 5 February 2019 (UTC)[reply]
Also regular polyhedron, regular polychoron, regular polyteron.  --Lambiam 23:23, 5 February 2019 (UTC)[reply]
And also regular tiling and even regular hyperbolic tiling.  --Lambiam 13:27, 6 February 2019 (UTC)[reply]
I don't see the relevance to these to the far more common collocation of "regular polygon". Compare my reference to stop sign above. We don't also have yield sign or speed limit sign or pedestrian crossing sign, so it doesn't follow that including one collocation forces the inclusion of the rest. bd2412 T 19:50, 6 February 2019 (UTC)[reply]
You argued above that the use of “regular” with respect to polygons is unique to those shapes. Well, as this list shows, it is not. A Google search for "regular polygon" reports about 731,000 results, while the search for "regular triangle"|"regular quadrilateral"|"regular pentagon"|"regular hexagon"|"regular heptagon"|"regular octagon" reports about 1,110,000 results. For "regular tetrahedron"|"regular hexahedron"|"regular octahedron"|"regular dodecahedron"|"regular icosahedron" Google search reports about 259,000 results. The search for "regular polytope"|"regular polyhedron"|"regular polychoron" yields another 106,000 results.  --Lambiam 05:20, 7 February 2019 (UTC)[reply]
FWIW, I consider yield sign fairly entry-worthy. Per utramque cavernam 20:07, 6 February 2019 (UTC)[reply]
It might be. However, speed limit sign and pedestrian crossing sign are probably not. bd2412 T 21:53, 6 February 2019 (UTC)[reply]
What is a yield sign anyway? A give way sign? DonnanZ (talk) 00:14, 10 February 2019 (UTC)[reply]
Answering my own question, yes, it's a give way sign. DonnanZ (talk) 00:28, 10 February 2019 (UTC)[reply]
Because the ambiguity of "regular" is such to render a definition of "regular polygon" necessary and useful. Purplebackpack89 05:18, 7 February 2019 (UTC)[reply]
Doesn’t the ambiguity of good, which can be used in a sentence like “It’s a good mile away”, then render a definition of “good mile” equally necessary and useful? If not, why not? Moreover, one can also say: “If you train hard you’ll be able to run a good mile”, so wouldn’t the ambiguity of “a good mile” then necessitate a definition of “a good mile away”?  --Lambiam 07:38, 10 February 2019 (UTC)[reply]
  • Keep It's a jargon in geometry. It could be said equilateral/equiangular polygon but no one did. Compare regular expression.--Octahedron80 (talk) 15:21, 10 February 2019 (UTC)[reply]
  • Delete, strongly. Reading the arguments previously made, I would have to throw out an argument like "too many meanings." And it isn't valid to compare an adjective-noun phrase "regular polygon" to a compound noun like "stop sign". The comparison with "regular expression" is better, but it truly is computer science jargon that cannot be understood by analyzing the individual components; whatever sense regular brings to the combination is not obvious from its other senses and is probably unique to "regular expression" (hence the need for the separate page). (I don't know if "the expression is regular" would be a valid statement, which could argue against what I just wrote.) By comparison regular in "regular polygon" has the clear sense of having equal sides and equal angles which applies not only to polygon but to many other (geometric) nouns as well. And "the polygon is regular" would be valid. I haven't seen any arguments good enough for keeping this phrase. -Mike (talk) 02:16, 11 February 2019 (UTC)[reply]
  • Keep: the meaning of "regular" employed is specific to polygons; thus, per talk:free variable rationale. If not that, redirect to regular. As an aside, note that star polygons are very regular but they are not what is meant by "regular polygon", which has to be convex. As for "regular expression", it would be a sum of parts if a corresponding definition would be placed to regular, of the form "(computing) of an expression, such that X". That is reminiscent of the red dwarf argument I made in talk:free variable. As for regular triangle, it could be created as well or it could be redirected to regular polygon since triangle is a species of polygon and the predicate "regular" when applied to a triangle is really inherited from polygon. On another note, I have no objections to placing label "sum of parts" at the beginning of the definition line so that the reader has a hint that they could figure it out themselves by looking up the component definitions. --Dan Polansky (talk) 10:32, 16 February 2019 (UTC)[reply]
I strongly disagree with a user-visible "sum of parts" label being applied to this or any other entry. Mihia (talk) 01:52, 17 February 2019 (UTC)[reply]
That's a statement of position; is there a rationale for that position? --Dan Polansky (talk) 06:14, 17 February 2019 (UTC)[reply]
I don't know about @Mihia, but I personally think it looks silly. Per utramque cavernam 08:47, 17 February 2019 (UTC)[reply]
For me, "sum of parts" is internal jargon that we use when discussing eligibility for inclusion. It seems inappropriate to make it visible to readers. Mihia (talk) 18:13, 17 February 2019 (UTC)[reply]
Having a SOP label would open up every adjective-noun combination to having its own page. I will also mention that Wikipedia disagrees with you. It says, "Regular polygons may be either convex or star." -Mike (talk) 09:38, 17 February 2019 (UTC)[reply]
It would not since the label would not introduce a policy that all attested SOP shall be included. As for the meaning, our definition excludes star polygons: "equiangular and equilateral (i.e. having all sides the same length and all interior angles the same", and this matches Mathworld[1]. --Dan Polansky (talk) 10:02, 17 February 2019 (UTC)[reply]
I don't see how "equiangular and equilateral (i.e. having all sides the same length and all interior angles the same)" excludes regular star polygons. Mihia (talk) 18:16, 17 February 2019 (UTC)[reply]
How can a star polygon have all interior angles the same, when half of the internal angles will be the opposite of the other half? bd2412 T 18:31, 17 February 2019 (UTC)[reply]
The true interior angles of a star polygon are the angles at the points of the star only. The additional angles created by the intersection of the sides of the polygon do not count. This is why the regular star polygons are truly regular polygons (albeit self-intersecting), and not a mixture of different edge lengths and angles. Mihia (talk) 18:44, 17 February 2019 (UTC)[reply]
Star polygon with intersecting sides
Star with non-intersecting sides, also a polygon
I see what you mean: you mean star polygons with intersecting sides whereas I meant star polygons with alternating angles and non-intersecting sides. Mathworld only shows the "ordinary" non-intersecting regular polygons on its images, no star polygons. --Dan Polansky (talk) 20:01, 17 February 2019 (UTC)[reply]
OK, I see what you mean. Yes, I am referring only to the self-intersecting ones. Mihia (talk) 20:06, 17 February 2019 (UTC)[reply]
If a polygon is "a plane figure bounded by edges that are all straight lines", doesn't that exclude shapes with intersecting lines from being polygons at all, since those lines wouldn't part of the edges by which the shape is bound? bd2412 T 22:21, 21 February 2019 (UTC)[reply]
Self-intersecting polygons are a recognised class of polygons. Mihia (talk) 00:23, 24 February 2019 (UTC)[reply]
Indeed they are. I stand corrected. bd2412 T 01:33, 26 February 2019 (UTC)[reply]


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