Talk:Blackboard bold

Why aren't the arabic letters included?
𞺡𞺢𞺣𞺥𞺦𞺧𞺨𞺩𞺫𞺬𞺭𞺮𞺯𞺰𞺱𞺲𞺳𞺴𞺵𞺶𞺷𞺸𞺹𞺺𞺻. 1234qwer1234qwer4 (talk) 12:21, 20 April 2019 (UTC)

They indeed need to be added, but I haven't an appropriate font to see what I'm doing with them. Please feel free to add, or, when I get sufficiently setup for such, I eventually will. TSamuel (talk) 14:10, 20 April 2019 (UTC)

Notable inclusion?
I know that "in fiction" sections are much less used these days, but I wanted to mention that "Blackboard Bold Uppercase Y" (𝕐) is an important character to the fictional SCP-𝕐, a popular work in the SCP Foundation wiki. 50.5.2.43 (talk) 16:48, 25 July 2022 (UTC)


 * If you find a reliable source that makes a concrete connection between the subject of this article and whatever it is you're talking about, then we could consider it; until then, definitely not. JBL (talk) 18:10, 25 July 2022 (UTC)

Universal Set
Hey guys! So I'm relatively new to Wikipedia, so I'm not entirely sure exactly what I'm supposed to do when. You see, I always represented the Universal Set with a 𝕌 symbol, so I edited this article to reflect that. Someone undid it, so I put it back up, but that wasn't the right thing for me to have done. Thank you to JayBeeEli for letting me know that I need to discuss it here. Now I am not 100% sure what sources are dubbed "reliable" and what are not, so I'm just gonna list a few sources here. Thanks! :>

https://www.symbols.com/symbol/universal-set

https://byjus.com/maths/universal-set/#:~:text=A%20universal%20set%20is%20a,by%20the%20symbol%20%27U%27.

https://www.mathsisfun.com/sets/symbols.html

https://www.redbubble.com/i/ipad-skin/Set-Theory-Symbols-by-coolmathposters/28080035.MHP6F

https://www.cuemath.com/algebra/universal-set/

Hope this helps! (Like I said, I'm relatively new here, so if I did something wrong, please let me know!! Also thanks again to JayBeeEli for letting me know to respond here! :D) The Wikepidea Animat0r (talk) 18:21, 8 June 2023 (UTC)


 * So... what happens now? Sorry, I'm still trying to get the hang of how to use Wikipedia and all that, so what happens next? Do we discuss the topic further or leave it at that? Thanks in advance! :D The Wikepidea Animat0r (talk) 19:12, 8 June 2023 (UTC)
 * Hi, thanks for starting the discussion here. Wikipedia doesn't have a deadline, and all its editors are (like you) volunteers, spread across the globe, so generally you shouldn't expect immediate responses.  As the person who reverted you, I was planning to wait a bit to see if any other editors respond before I give my opinion.  (And if it turns out after a few days that this discussion doesn't attract any interest from other editors, we can always try to recruit some other opinions at Wikiproject Math.)  --JBL (talk) 19:28, 8 June 2023 (UTC)
 * @The Wikepidea Animat0r – I don't know if I would consider any of those webpages to be "reliable sources" by Wikipedia standards, though I didn't look super closely. One good way to find sources is to search in a citation index such as Google Scholar. Here's an example search https://scholar.google.com/scholar?q=%22universal+set%22 but I didn't try reading to figure out if any of those use the blackboard bold symbol. –jacobolus (t) 03:39, 26 July 2023 (UTC)
 * @The Wikepidea Animat0r, I did some searching in the academic literature and I can't find any examples of people using $$\mathbb{U}$$ for universal set (though I do find several papers which use the ordinary upper-case italic $$U$$ for this purpose). Can IP editors please stop adding this back to the article, unless you have a clear source? Ideally we wouldn't add symbol associations here unless there is widespread usage, as many individual papers invent new notation for local convenience: the ideal is a secondary source which explicitly says something like "the symbol XYZ is traditionally used to mean foobar", but in edge cases I can imagine making do with a discussion involving a substantial enough list of primary sources demonstrating common usage, since this is the kind of thing secondary sources don't necessarily bother to explicitly discuss. (cf. Reliable sources.) –jacobolus (t) 15:11, 28 September 2023 (UTC)
 * Hey there @Jacobolus! I'm not sure if this counts, but www.mathsisfun.com is a reliable website, and it uses the blackboard bold U as the universal set: https://www.mathsisfun.com/sets/symbols.html The Wikepidea Animat0r (talk) 19:54, 28 September 2023 (UTC)
 * I see no reason to think that www.mathsisfun.com is a reliable website. But also your response doesn't address the meat of jacobolus's comment, with which I agree strongly.  --JBL (talk) 20:14, 28 September 2023 (UTC)
 * @The Wikepidea Animat0r can you find academic papers, monographs, or textbooks using the symbol this way? –jacobolus (t) 20:27, 28 September 2023 (UTC)
 * @Jacobolus @JayBeeEll Hey guys! I think I've found a pretty reliable source that explicitly mentions using a blackboard bold U as the universal set. (page 6) https://staffwww.dcs.shef.ac.uk/people/A.Simons/z2sal/zdocs/ISO_Z%202002.pdf
 * Does this fit the criteria of something to prove the use of this notation? Thanks in advance guys! :D The Wikepidea Animat0r (talk) 17:19, 19 December 2023 (UTC)
 * I thought that since it's an ISO standard, it could be a reliable source. The Wikepidea Animat0r (talk) 17:21, 19 December 2023 (UTC)
 * @Jacobolus @JayBeeEll I also found another source that explicitly states using a blackboard bold U as the universal set: https://hydraulics.unibs.it/hydraulics/wp-content/uploads/2014/02/Math_symbols.pdf The Wikepidea Animat0r (talk) 22:32, 27 January 2024 (UTC)
 * Rapidtables.com is not a "reliable source". –jacobolus (t) 22:37, 27 January 2024 (UTC)
 * This ISO standard is a better source than the others you found. To quote: "The universe, $\mathbb{U},$ denotes a world of sets, providing semantic values for Z expressions. $\mathbb{U}$ is big enough to contain the set from which Z names are drawn, and an infinite set. Also, $\mathbb{U}$ is closed under formation of powersets and products. The formation of a suitable $\mathbb{U}$ comprising models of sets and tuples, as needed to model Z, is well-known in ZF set theory and is assumed in this International Standard." This isn't really a claim about what the $$\mathbb{U}$$ generally stands for, but at least it's an example of the symbol being used (though I'm not entirely clear on the relation between "universe" or "world of sets" vs. "universal set"). –jacobolus (t) 00:14, 28 January 2024 (UTC)

Twitter Logo
I imagine this article is about to get a lot of attention and a flood of edits in light of Musk's announcement that the new Twitter/X Corp logo is one of the symbols on this page. Do we think it's newsworthy enough to add or not? 74.64.100.109 (talk) 14:54, 24 July 2023 (UTC)


 * No, it does not need to be mentioned. You can write about this topic at Twitter under Elon Musk. –jacobolus (t) 15:12, 24 July 2023 (UTC)

Hatnote
@Tamzin – there has been a momentary large (relative to background levels for the same page) spike in people visiting Blackboard bold and also a lower spike in people visiting the newly created 𝕏 redirect, but there's no evidence that people are going there to find out about Twitter. More likely, people are wondering "what in the world is blackboard bold" or "what in the world is this unicode 𝕏 character". Whatever quick blip we got from social/traditional media attention is going to die off within days, and there's really no significant value in adding a hatnote here. Readers trying to find out about Twitter, X Corp., Elon Musk, etc. are very unlikely to try to find it via an obscure Unicode glyph, nor are they likely to have any trouble finding those via the direct page titles.

I think it's bad form to include a hatnote because we could just as well include one for every other blackboard bold letter (there are many corporate logos, etc. which look like various hollowed-out letters), but it starts to get ridiculous. Someone can easily find X or X (disambiguation) (or substitute your favorite other letter) if they need to find random other uses of these English letters. –jacobolus (t) 21:31, 26 July 2023 (UTC)


 * For context, here are page view statistics for a bunch of relevant pages (click 'log scale' to better see some of the smaller values). –jacobolus (t) 21:34, 26 July 2023 (UTC)
 * There is widespread coverage    of Twitter using a specific typeset's version of the Unicode doublestruck X as its logo, and the Unicode glyph is being used to represent Twitter. People—such as Victor LP, creator of the redirect originally pointing to Twitter—are absolutely typing "𝕏" expecting to get some kind of content about the Twitter rebrand. And, per WP:RECENTISM, we shouldn't give them that directly, i.e. we shouldn't have the glyph redirect to Twitter. But "𝕏" is a valid alias for Twitter, and WP:HATNOTERULES #4 is clear: When a name for something does not lead to the article on thing, there must be a hatnote linking users to the relevant article or a DAB. Hatnotes, especially section-level hatnotes, are cheap—readers just skim past them if irrelevant—so I don't see why this is a big deal. There are probably hundreds of thousands of hatnotes across Wikipedia for less notable alternate meanings.  --  Tamzin  [ cetacean needed ] (she&#124;they&#124;xe) 22:40, 26 July 2023 (UTC)
 * 𝕏 is not an "alias for twitter". 𝕏 is a "symbol that looks approximately similar to the 'placeholder' logo Elon Musk recently imposed at twitter, which is (maybe soon but not actually yet) being renamed to 'X'" (note, not 'double-struck X' but just 'X'). –jacobolus (t) 00:17, 27 July 2023 (UTC)
 * "𝕏" is a plausible search term for someone looking for Musk's rebranding of Twitter. Furthermore, discusses the use of the glyph. Thus it should have a hatnote. It is as simple as that. There is literally no downside here, while even a marginal benefit to readers (and I'd say this is well more than marginal) justifies using a hatnote.  --  Tamzin  [ cetacean needed ] (she&#124;they&#124;xe) 01:22, 27 July 2023 (UTC)
 * You'll notice that Twitter does not even link to this page, nor does it directly mention 𝕏 –jacobolus (t) 01:44, 27 July 2023 (UTC)
 * It did mention it, just not by name. Which is bad writing, so I've remedied that by adding unichar and a wikilink to this article. --  Tamzin  [ cetacean needed ] (she&#124;they&#124;xe) 02:04, 27 July 2023 (UTC)
 * As follow-up here, @Tamzin, notice that 2 months later all of these terms |Blackboard_bold|X_Corp.|𝕏|Acquisition_of_Twitter_by_Elon_Musk have now fallen back from the peak to roughly (within 30% or so) their pre-spike baseline level of viewership (tick log scale), with "𝕏" typically getting a mere handful of views. –jacobolus (t) 14:59, 28 September 2023 (UTC)

Sources for the 'usage' section
Could someone try to track down specific references for ? Right now we have a lot of plausible but unsourced claims there about which symbol is used for what. –jacobolus (t) 00:32, 28 July 2023 (UTC)