\begin{definition}[Definition:Formal Grammar/Bottom-Up/Extremal Clause]
Let $\FF$ be a formal language.
Let the rules of formation of $\FF$ be defined in a bottom-up manner.
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The '''extremal clause''' of a bottom-up grammar is the final rule which excludes all collations other than those specified in the formation rules from being well-formed formulas.
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\end{definition}