[[Material set theory]]
# Emptyset axiom

The **Emptyset Axiom** is a possible axiom in [[Material set theory]]: #m/def/set/zf 
$$
\begin{align*}
(\exists \shood o)(\nexists x)[x \in o]
\end{align*}
$$
which is to say, there exists a set with no elements,
which by the [[Axiom of Extensionality]] is unique and may be called $\0$, the [[empty set]].

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#state/tidy | #lang/en | #SemBr