Unicode notation of Euler Constant

Question

According to Wikipedia, eulers-constant is usually denoted as $\gamma$. Why does Unicode use 'ℇ' to denote this number?

Wikipedia redirects 'ℇ' to eulers-constant, but in that page, there's no mention of Unicode.

Are both notation accepted? Which one is better?

Answer 1

One conversation about the symbol on the talk page corresponding to the page for Euler's constant on Wikipedia led me to another where the link you discovered was first put into place. That other discussion also gave the clue that this is related to an old Xerox standard "XCCS 353/046". Searching for that, led me to an archive of a conversation about Unicode back in 2002 where Ken Whistler, a technical director for Unicode said the following:

The source for this character is XCCS 353/046 "Euler's". That Xerox standard didn't say Euler's what, however. And the character committees just added "CONSTANT" to it.

So, to summarize:

• For reasons unknown (I can't find any more detail online), an old Xerox standard had a table of characters with something like ℇ on it labeled "Euler's"
• Early Unicode committee(s) thought it might be distinct from other forms of "E", and figured it was some constant of Euler's so made ℇ and labeled it "Euler Constant". But it's unclear whether they had in mind Euler's number $e$ or the Euler-Mascheroni constant $\gamma$.
• Someone editing Wikipedia, having in mind the sometimes-followed convention that "Euler's constant" is $\gamma$ and not $e$, decided to make ℇ link to the page for $\gamma$.
• That was never undone, despite the facts that: As far as I can tell, no one uses ℇ for $\gamma$. Since ℇ looks like $E$ or $\varepsilon$, that suggests $e$ is more likely than $\gamma$ as the original intent of the Xerox standard.