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<p>denotes the sentence formed by <a href="page.php?w=logical_conjunction">logical conjunction</a>  then  and  where  If  is the <a href="page.php?w=Lindenbaum-Tarski_algebra">Lindenbaum-Tarski algebra</a> associated with  then  is a partially ordered set that is also a directed set.</p>

<p><big>Contrast with semilattices</big></p>
<p>Directed set is a more general concept than (join) semilattice: every <a href="page.php?w=Semilattice">join semilattice</a> is a directed set, as the join or least upper bound of two elements is the desired   The converse</p><p>
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