hat is, a set whose elements are sets—then</p>
<div class="quote">
<p><span class="math inline">\(\bigcap \mathcal{F} = \{x \mid \forall A(A \in \mathcal{F} \to x \in A)\} = {}\)</span> the <em>intersection</em> of the family <span class="math inline">\(\mathcal{F}\)</span>,</p>
<p><span class="math inline">\(\bigcup \mathcal{F} = \{x \mid \exists A(A \in \mathcal{F} \wedge x \in A)\} = {}\)</span> the <em>union</em> of the family <span class="math inline">\(\mathcal{F}\)</span>.</p>
</div>
<p>Finally, Ch