\define .operator-rows(filter)
<$list filter="$filter$"><tr>
<td><$link to={{!!title}}>{{!!caption}}</$link></td>
<td>{{!!op-purpose}} <$list filter="[all[current]tag[Common Operators]]">{{$:/core/images/done-button}}</$list></td>
<td align="center"><$list filter="[all[current]tag[Negatable Operators]]">`!`</$list></td>
</tr></$list>
\end

\define .group-heading(_)
<tr class="doc-table-subheading"><th colspan="3" align="center">$_$</th></tr>
\end

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.

<table>
<tr>
<th align="left">Operator</th>
<th align="left">Purpose</th>
<th align="left">Neg</th>
</tr>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Order Operators">>
<<.operator-rows "[tag[Filter Operators]tag[Order Operators]!tag[Listops Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Listops Operators">>
<<.operator-rows "[tag[Filter Operators]tag[Listops Operators]tag[Order Operators]!tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "String Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]tag[String Operators]!tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Tag Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[String Operators]tag[Tag Operators]!tag[Special Operators]sort[]]">>
<<.group-heading "Special Operators">>
<<.operator-rows "[tag[Filter Operators]!tag[Order Operators]!tag[String Operators]!tag[Tag Operators]tag[Special Operators]sort[]]">>
</table>

A typical step is written as `[operator[parameter]]`, although not all of the operators need a [[parameter|Filter Parameter]].

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]].