View source for ∅

{{also|∅-|-∅|Ø|⌀|ø|uni=auto}}
{{character info}}
{{character info|⦰}}
{{character image|Unicode 0x2205, cv98.svg|caption=A slashed-zero variant is [[variation selector|forced with]] ⟨&amp;#xFE00;⟩ in a supporting font.}}
==Translingual==
{{wp|Empty set}}
{{wp|Zero (linguistics)}}
{{wp|Diameter#Symbol|Diameter (symbol)}}

===Etymology===
The set-theoretic meaning of this symbol was introduced by the [[w:Nicolas Bourbaki|Bourbaki group]] in their treatise ''[[w:Éléments de mathématique|Éléments de mathématique]]''. [[w:André Weil|André Weil]] has said in his autobiography that he based it on the {{der|mul|no|-}} letter {{l|no|ø|Ø}}.<ref>A. Weil, ''The Apprenticeship of a Mathematician'', chapter V "Strasbourg and Bourbaki", p. 114; Birkhäuser Verlag 1992</ref>

===Symbol===
{{head|mul|symbol|sc=Zsym}}

# {{lb|mul|set theory}} A set with no elements: the [[empty set]].
#: {{syn|mul|&lcub; &rcub;|&lcub;&rcub;}}
# {{lb|mul|linguistic morphology}} A [[null morpheme]]; a theoretical [[morpheme]] used in models of [[linguistic]] [[analysis]] to represent the absence of a morpheme where one might otherwise be expected.

====Usage notes====
Unicode enables a variant <math>\emptyset</math> that looks like a slashed zero, [[0︀]], by following ∅ with [[variation selector|Variation Selector 1]] (U+FE00).<ref name="emptyset">https://www.unicode.org/L2/L2015/15268-slashed-zero.pdf</ref>

===See also===
* {{l|mul|∅-}} {{q|the [[zero prefix]]}}
* {{l|mul|-∅}} {{q|the [[zero suffix]]}}
* {{l|en|null determiner}}

===References===
<references/>

==Vietnamese==

===Etymology===
From the empty set symbol.

===Adjective===
{{vi-adj}}

# {{abbreviation of|vi|trống|t={{l|en|empty}}}}