[FOM] Slashed circle symbol for the empty set

Howard, William A. wahow at uic.edu
Fri Apr 3 20:55:50 EDT 2009

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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