= Unimodal function
A real <function> on an interval is <unimodal function>[unimodal] if there is a point $m$ such that it is nondecreasing to the left of $m$ and nonincreasing to the right. This convention describes a single peak and allows flat regions. Some optimization texts instead use the corresponding single-valley convention, so the direction must be specified.
For example, $f(x)=-(x-2)^2$ has its peak at $2$. A unimodal density can describe a distribution with one mode, while unimodality of an objective allows interval-elimination search methods. <Concavity> implies peak unimodality, but unimodality alone does not require the chord inequalities of <concavity>.
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