[FOM] RE : Slashed circle symbol for the empty set

BEZIAU Jean-Yves jean-yves.beziau at unine.ch
Sat Apr 4 09:53:17 EDT 2009

It is true that this symbol for the empty set is due to Weil.
I think the explanation is just that Andre Weil was at the time in Norway, saw this letter and thought intuitively that this was a nice symbol to represent the empty set.
You can have a look at the autobiography of Weil translated into English:
The Apprenticeship of a Mathematician, Birkhauser, Basel 1992

Jean-Yves Beziau.
De : fom-bounces at cs.nyu.edu [fom-bounces at cs.nyu.edu] de la part de Howard, William A. [wahow at uic.edu]
Date d'envoi : samedi, 4. avril 2009 02:55
À : fom at cs.nyu.edu
Objet : [FOM] Slashed circle symbol for the empty set

Someone just told me that the empty set symbol resembling a slashed small
circle was chosen from the Norwegian alphabet by Andre Weil. Does anyone
know whether this is true, and, if so, why Weil chose this symbol?

In any case, I had always assumed that the use of this symbol was
motivated by the idea that one wants a suggestive symbol for the "zero
set"; but, of course, the "obvious" reason need not be the historical

Bill Howard

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