06A06-UpperBound.tex

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Let $S$ be a set with a partial ordering $\leq$, and let $T$ be a subset of $S$. 
An {\em upper bound} for $T$ is an element $z \in S$ such that $x \leq z$ for all $x \in T$. We say that $T$ is {\em bounded from above} if there exists an upper bound for $T$.

{\em Lower bound}, and \emph{bounded from below} are defined in a similar manner.
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