Editing 2606: Weird Unicode Math Symbols

{{comic
| number    = 2606
| date      = April 13, 2022
| title     = Weird Unicode Math Symbols
| image     = weird_unicode_math_symbols.png
| titletext = U+2A0B ⨋ Mathematicians need to calm down
}}

==Explanation==
This comic proposes joke explanations for various {{w|unicode symbols}} with obscure or no known uses, see the [[#Table of symbols|table]] below. 

It may have been inspired by this blog post [https://ionathan.ch/2022/04/09/angzarr.html U+237C ⍼ RIGHT ANGLE WITH DOWNWARDS ZIGZAG ARROW]. It was posted four days prior to this comic's release. The blog post went viral (in a limited sense) the same day the comic was published, perhaps as a consequence of it mentioning one of the symbols of the comic, Larry Potter. This caused the blogger to update his post with a [[33: Self-reference|reference]] to both xkcd and explain xkcd: 
:"XKCD #2606 mentions ⍼ and its Explain XKCD entry cites this post"

The title text includes yet another special symbol ⨋, and this symbol prompts [[Randall]] to ask Mathematicians to calm down. See more details in the table below, where the title text symbol is mentioned in the last entry.

===Table of symbols===
{| class="wikitable"
|+ Symbols
|-
! Codepoint !! Symbol !! Unicode Name !! Actual use !! Randall's meaning || Explanation
|-
| U+29CD || <span style="font-size: xx-large;">⧍</span> || Triangle with Serifs At Bottom || No known mathematics use, but resembles the {{w|National Park Service}} cartographic symbol for a campsite.[https://github.com/nationalparkservice/symbol-library/] || Shark || May look like a shark fin sticking out of the water.
|-
| U+23E7 || <span style="font-size: xx-large;">⏧</span> || Electrical Intersection || Indicates where wires branch off || Traffic circle || Looks like a diagram of a {{w|roundabout}} as might be shown on a minimap beside a routing direction.
|-
| U+2A33 || <span style="font-size: xx-large;">⨳</span> || {{w|Smash product}} || The quotient of the product of the underlying spaces of two {{w|pointed space}}s, where points in the {{w|product space}} are identified if they contain either labeled point as an element. || <span style="letter-spacing: 0.1em;"><span style="transform: rotate(-45deg); display: table-cell;">H</span><span style="transform: rotate(-45deg); display: table-cell;">a</span><span style="transform: rotate(-45deg); display: table-cell;">s</span><span style="transform: rotate(-45deg); display: table-cell;">h</span><span style="transform: rotate(-45deg); display: table-cell;">t</span><span style="transform: rotate(-45deg); display: table-cell;">a</span><span style="transform: rotate(-45deg); display: table-cell;">g</span></span> || Looks somewhat like the {{w|Number sign|hash}} symbol (#) – commonly used for indicating tags called {{w|hashtag}}s in social media – turned by 45 degrees.
|-
| U+2A7C || <span style="font-size: xx-large;">⩼</span> || Greater-Than with Question Mark Above || Used in proofs to indicate a greater-than relation that should exist but hasn't been proven yet (non-rigorous) || Confused alligator || One metaphor used when teaching inequality signs in primary school is that the sign looks like an alligator mouth "eating" the larger number. Question marks are commonly used in cartoons to indicate confusion on the part of a character.
|-
| U+299E || <span style="font-size: xx-large;">⦞</span> || Angle with S Inside || Plural for the angle symbol (∠) [https://www.quora.com/Unicode-How-is-the-s-in-triangle-glyph-used-in-mathematics][https://www.birdvilleschools.net/cms/lib2/TX01000797/Centricity/Domain/1114/Homework%20Helper%20Unit%203%20ch%209-10.pdf] rarely used || Snack || May look like a mouth eating an S, where the S symbolizes some snack food, or the word "snack".
|-
| U+2A04 || <span style="font-size: xx-large;">⨄</span> || {{w|Arity|N-ary}} Union Operator with Plus || Disjoint union[https://books.google.com/books?id=531cAgAAQBAJ&pg=PA165&lpg=PA165&dq=%E2%A8%84&source=bl&ots=oYXkMNXP-T&sig=ACfU3U2QvMRBkD7uVG0OSumKI0JQtjTIKA&hl=en&sa=X&ved=2ahUKEwios862ypL3AhWXVTABHTnQALQQ6AF6BAgKEAM] (joining a family of sets that have no elements in common) || Drink refill || Looks like a cup with a plus to indicate adding drink to the cup.
|-
| U+2B48 || <span style="font-size: xx-large;">⭈</span> || Rightwards Arrow Above Reverse Almost Equal To || Pairs with <span style="font-size: x-large;">⭂</span> which could conceivably mean {{w|Assignment (computer science)|assignment}} of an {{w|Approximation|approximation}}, but neither seem to be in use. Possibly intended to describe ill-defined projections. || Snakes over there || Looks like two squiggles to represent snakes and an arrow indicating the direction where they may be found.
|-
| U+225D || <span style="font-size: xx-large;">≝</span> || Equal To By Definition || Indicates an equation where the left side is to be defined as the right side[https://www.reddit.com/r/math/comments/1z1mty/can_someone_please_explain_the_equal_to_by/] usually used in proofs to indicate a definition is being introduced|| Definitely, for sure || "Def" is a contraction of "definitely" used in slang; the equal sign looks like a double underline, indicating heavy emphasis.
|-
| U+237C || <span style="font-size: xx-large;">⍼</span> || Right Angle with Downwards Zigzag Arrow || No purpose is known.[https://ionathan.ch/2022/04/09/angzarr.html] Speculation includes a diode with a gate, proof by contradiction, a proofreaders' mark to split a word, and indication of polarization direction. || Larry Potter || Looks like the letter "L" and a lightning bolt. {{w|Harry Potter (character)|Harry Potter}} is known for having a lightning bolt-shaped scar on his forehead.  The character {{w|Legal_disputes_over_the_Harry_Potter_series#Nancy_Stouffer|Larry Potter}} figured in a fraudulent legal claim against J.K. Rowling.
|-
| U+2A50 || <span style="font-size: xx-large;">⩐</span> || Closed Union with Serifs and Smash Product || Indicates that a collection of topological spaces is {{w|Union-closed sets conjecture|closed}} when taking arbitrary unions and smash products. That is, if you take the union of any collection of topological spaces in the collection (even uncountably many), or the smash product of them, the result will also be in that collection. This is apparently important because the sets can't be isomorphic (one cannot be rearranged to be exactly the other.) [https://mathoverflow.net/questions/196084/counterexample-for-associativity-of-smash-product] || Spider caught with a cup and index card || Spiders or other bugs found within someone's house or workspace may be caught with a glass and something flat, often a card or a magazine, to be released outside. The projecting lines of the smash product symbol resemble the legs of a spider. Confusingly, some fonts display this symbol with different numbers of "legs": eight, as a 45°-rotated hash symbol, or six as an asterisk.
|-
| U+2A69 || <span style="font-size: xx-large;">⩩</span> || Triple Horizontal Bar with Triple Vertical Stroke || Emblem of the Romanian {{w|Iron Guard}} fascist political movement
<!--

Salve o popolo d'eroi Salve o Patria immortale Son rinati i figli tuoi Con la fede e l'ideale<br>
Il valor dei guerrieri La vision dei pionieri La vision dell'Alighieri Oggi brilla in tutti i cuor<br>
Giovinezza, giovinezza Primavera di bellezza Nella vita e nell'asprezza Il tuo canto squilla e va <br>
Dell'Italia nei confini Son rifatti gli italiani Li ha rifatti Mussolini Per la guerra di domani<br>
Per la gioia del lavoro Per la pace e per l'alloro Per la gogna di coloro Che la Patria rinnegar <br>
Giovinezza, giovinezza Primavera di bellezza Nella vita e nell'asprezza Il tuo canto squilla e va<br>
I poeti e gli artigiani I signori contadini Con orgoglio di italiani Giuran fede a Mussolini<br>
Non v'è povero quartiere Che non mandi le sue schiere Che non spieghi le bandiere Del fascismo redentor<br>
Giovinezza, giovinezza Primavera di bellezza Nella vita e nell'asprezza Il tuo canto squilla e va<br>
Giovinezza, giovinezza Primavera di bellezza Nella vita e nell'asprezza Il tuo canto squilla e va<br>
-->; Loosely [http://molview.org/?q=CC1(C)C2(C)C(C)(C)C3(C)C24C1(C)C(C)(C)C4(C)C3(C)C resembles] part of the {{w|International Association for Cryptologic Research|IACR}} logo, as depicted in [[153: Cryptography]]; possibly a four-by-four {{w|tic-tac-toe}} board.[https://pages.cs.wisc.edu/~sandlund/NumericalTicTacToe.pdf] || ℍ𝕒𝕤𝕙𝕥𝕒𝕘 || Hash symbol with one extra vertical and horizontal line, or perhaps a hash symbol which has been accidentally double-struck or overprinted.
|-
| U+2368 || <span style="font-size: xx-large;">⍨</span> || APL Functional Symbol Tilde Diaeresis || Used for a two-argument operation to [https://aplwiki.com/wiki/Commute commute] (swap) its arguments or allow it to use a single provided argument in both argument slots, and to convert a value into a [https://aplwiki.com/wiki/Constant constant] function || <span style="font-size: large;">:/</span> || Looks like a confused or disappointed face. Randall's use is in fact common among {{w|APL (programming language)|APL}} programmers in the comments, as documented [https://aplwiki.com/wiki/APL_Orchard#Emoticons here] and [https://aplwiki.com/wiki/Humour#Glyph_puns here].
|-
| U+2118 || <span style="font-size: xx-large;">℘</span> || Script Capital [''sic''] P || A stylized {{w|round hand}} 'p' used by Weierstrass for his "{{w|Weierstrass elliptic function|p-function}}," with features of both capital 𝒫&nbsp; and small 𝓅. Sometimes also used as the {{w|power set}} operator.
|| Snake || This symbol coils around like a long snake, with a tapering-off tail on one end and a small "head" on the other.
|-
| U+2AC1 || <span style="font-size: xx-large;">⫁</span> || Subset with Multiplication Sign Below || Indicates that one set is subset of another by means of a product || <div style="writing-mode: vertical-rl; text-align: center;">User<br />experience</div> || Looks like the letters "Ux" sideways; UX is a common abbreviation for {{w|user experience}}.
|-
| U+232D || <span style="font-size: xx-large;">⌭</span> || {{w|Cylindricity}} ||  A symbol used in geometric dimensioning and tolerancing (GD&T) to represent a parameter called "cylindricity" which describes the statistical deviation of an ensemble of surfaces from a reference cylinder. [https://cimquest-inc.com/metrology-minute-cylindricity/ example use] || Rolling dough between your hands to shape it into a ball || Looks like two flat hands (perhaps like stick-figure arms) rolling a ball between them. Rolling dough between one's hands to make it into a ball is an important step in making many kinds of pastry and bread.
|-
| U+2A13 || <span style="font-size: xx-large;">⨓</span> || Line Integration with Semicircular Path Around Pole || Very rare symbol for half of a closed {{w|Contour integration|contour}} or {{w|Line integral|line}} integral which contains the {{w|Origin (mathematics)|origin}} in its interior. Contour integrals which circle the origin are very important in complex analysis. If such an integral were split into two parts, each could be represented by this symbol (which can be mistaken for <span style="font-size: x-large;">⨔</span>, the integral not including the {{w|Zeros and poles|pole}}, with a wider and more complete arc around an offset dot.) [https://math.stackexchange.com/questions/2299363/where-is-the-%E2%A8%93-integral-symbol-defined]
|| Integral that avoids a bee on the whiteboard || Looks like an {{w|integral}} symbol with a bump that goes around a dot, as if a professor was drawing an integral on a whiteboard but did not want to disturb a bee that had landed right in the path of their marker.
|-
| U+2A0B (title text)|| <span style="font-size: xx-large;">⨋</span> || Summation with Integral || The sum of the sum of the discrete elements (∑) and the integrals (∫) over the connected pieces. This symbol requires context to be meaningful but could occur, for instance, when computing probabilities using mixed distributions.
[https://twitter.com/fermatslibrary/status/1308743505309822977 see also] 
|| Mathematicians need to calm down || Each of the two symbols is specifically used to represent a kind of summation that is calculated completely differently from the other. Combining them could produce frustration for people unfamiliar with the usage. The comment given may make fun of mathematicians' tendency to form increasingly complex expressions in their work. It may as well be a pun on the pronounciation of the letter {{w|Esh_(letter)|Esh}} (Shhhh).
|-
|}

==Transcript==
<big>Weird Unicode Math Symbols</big>
<p>And their meanings</p>

{|
| U+29CD || ⧍ || Shark
|-
| U+23E7 || ⏧ || Traffic circle
|-
| U+2A33 || ⨳ || [The word "hashtag" with the letters slanted counterclockwise]
|-
| U+299E || ⦞ || Snack
|-
| U+2A04 || ⨄ || Drink refill
|-
| U+2B48 || ⭈ || Snakes over there
|-
| U+225D || ≝ || Definitely, for sure
|-
| U+237C || ⍼ || Larry Potter
|-
| U+2A50 || ⩐ || Spider caught with a cup and index card
|-
| U+2A69 || ⩩ || [The word "hashtag" but with extra horizontal and vertical lines]
|-
| U+2368 || ⍨ || :/
|-
| U+2118 || ℘ || Snake
|-
| U+2AC1 || ⫁ || [The words "user experience" rotated clockwise 90 degrees]
|-
| U+232D || ⌭ || Rolling dough between your hands to shape it into a ball
|-
| U+2A13 || ⨓ || Integral that avoids a bee on the whiteboard
|}

{{comic discussion}}
[[Category:Unicode]]
[[Category:Math]]
[[Category:Harry Potter]]