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As goatheard learns his trade by goat, so writer learns his trade by wrote.
FrontPage › EmptySetSymbol
공집합 기호에 관한 이런저런 자료 모음

  1. [U+2205]

  2. Computer Modern Math Symbol의 정의 (from Knuth's symbol.mf)
cmchar "Empty set symbol";
beginchar(oct"073",9u#,body_height#,body_height#-asc_height#);
adjust_fit(0,0);
penpos1(vair,90); penpos3(vair,-90); penpos2(stem,180); penpos4(stem,0);
if not monospace: interim superness:=sqrt(more_super*hein_super); fi
x2r=hround max(.7u,1.45u-.5stem);
x4r=w-x2r; x1=x3=.5w; y1r=asc_height+o; y3r=-o;
y2=y4=.5asc_height-vair_corr; y2l:=y4l:=.52asc_height;
penstroke pulled_arc.e(1,2) & pulled_arc.e(2,3)
 & pulled_arc.e(3,4) & pulled_arc.e(4,1) & cycle;  % bowl
pickup rule.nib; lft x6=hround 2u-eps; x5=w-x6; top y5=h+o; bot y6=-d-o;
draw z5--z6;  % diagonal
penlabels(1,2,3,4,5,6); endchar;
\Huge $\emptyset$

The null set symbol (Ø) first appeared in N. Bourbaki Éléments de mathématique Fasc.1: Les structures fondamentales de l'analyse; Liv.1: Theorie de ensembles. (Fascicule de resultants) (1939): "certaines propriétés... ne sont vraies pour aucun élément de E... la partie qu’elles définissent est appelée la partie vide de E, et designée par la notation Ø." (p. 4.)

André Weil (1906-1998) says in his autobiography that he was responsible for 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 modifications 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 Ø 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 from the French by Jennifer Gage. The citation was provided by Julio González Cabillón.

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

  1. Wikipedia
  2. 기호 구별
    \Huge $\emptyset, \varnothing, \phi$, \rlap{/}o, \o, \O
    1. $\emptyset$ ($\emptyset$) TeX의 cm 수학 글꼴의 공집합 기호.
    2. $\varnothing$ ($\varnothing$) AMSTeX의 대체 공집합 기호. 다른 기호와 다른 점은 정확한 원에 사선을 그은 것이다.
    3. $\phi$ ($\phi$) 그리스 소문자 phi.
    4. $\rlap{/}o $ 영문 소문자 o에 슬래시를 합친 것.
    5. $\o, \O $ 터키어, 핀란드어, 노르웨이어, 스웨덴어, 덴마크어 등의 알파벳 중 하나. oe의 리가처.
    6. ⌀ ([U+2300]) 지름을 나타내는 단위 기호.


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