RE: IPA Null Consonant

From: Kent Karlsson (
Date: Thu May 29 2003 - 10:01:22 EDT

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    Michael Everson wrote:
    > >(Remember that the empty set symbol really was an O with stroke,
    > >originally!)
    > Surely a 0 with stroke, not a O with stroke.

    The empty set sign was originally definitely the Norwegian/Danish letter
    CAPITAL O WITH STROKE. It never was related at all to a ZERO with

    See (which I referred to
    though it unfortunately uses the term "null set"...; but it also (quite
    uses U+00D8 for the empty set symbol, rather than U+2205; the choice is

    The null set symbol (Ř). André Weil (1906-1998) says in his
    that he introduced the symbol:

            Wisely, we had decided to publish an installment establishing
    the system
            of notation for set theory, rather than wait for the detailed
    treatment that
            was to follow: it was high time to fix these notations once and
    for all, and
            indeed the ones we proposed, which introduced a number of
            to the notations previously in use, met with general approval.
    Much later, my
            own part in these discussions earned me the respect of my
    daughter Nicolette,
            when she learned the symbol Ř for the empty set at school and I
    told her that
            I had been personally responsible for its adoption. The symbol
    came from the
            Norwegian alphabet, with which I alone among the Bourbaki group
    was familiar.

    The citation above is from page 114 of André Weil's The Apprenticeship
    of a
    Mathematician, Birkhaeuser Verlag, Basel-Boston-Berlin, 1992. Translated
    the French by Jennifer Gage. The citation was provided by Julio González

    This letter is used in the Norwegian, Danish and Faroese alphabets.

                    /kent k

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