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A <<.def "filter operator">> is a predefined keyword attached to an individual [[step|Filter Step]] of a [[filter|Filters]]. It defines the particular action of that step.
The following table lists all the core operators. The commonest ones are checkmarked. The third column indicates which operators allow <$link to="Filter Step">the <code>!</code> prefix</$link> to reverse their meaning.
Most steps process the [[selection of titles|Title Selection]] that are supplied as their input, but a few [[construct an entirely new selection|Selection Constructors]] instead. For the exact rules, see [[Filter Syntax]].