Re: Empty set

From: Stephan Stiller <>
Date: Thu, 12 Sep 2013 11:38:29 -0700

> The notation { } is quite correct. It just isn’t an atomic symbol for
> the empty set but an expression consisting of the two characters “{”
> and “}”, with a list (here, an empty list) of elements between them.
Reminds me of typographically composite stuff that has its own scalar
value ("code point") now:
     := is ≔
     ... is …
(Yes, they're different because they're semantically atomic, unlike { }.)

I was just browsing Bourbaki's "Éléments", and saw ∅ there. I wasn't
sure because Springer uses LaTeX for a lot of things now, which has both
\emptyset (producing something resembling the German variant, a
struck-through zero, though I know many of the German resources I looked
at didn't use LaTeX) and \varnothing (producing ∅). But this
> Regarding the empty set, the page
> rather convincingly attributes the symbol to André Weil, who says that
> it was inspired by the Norwegian letter “Ø”.
clarifies all.

Received on Thu Sep 12 2013 - 13:40:22 CDT

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