diff --git a/templates/de/about.html.ep b/templates/de/about.html.ep
index c58aebf..e58acd2 100644
--- a/templates/de/about.html.ep
+++ b/templates/de/about.html.ep
@@ -9,6 +9,34 @@
     Die hier verwendeten Modelle beruhen zum einen auf einer Erweiterung von word2vec (Mikolov et al. 2013), wang2vec (Ling et al. 2015)
     und zum anderen auf einfachen Kookkurrenzhäufigkeiten und Analysemethoden, die auf diesen operieren.
 </p>
+<h3>Suchanfragen</h3>
+<p>
+    Mehrere durch Leerzeichen getrennte Wortformen werden zu einem Suchvektor addiert, es wird
+    also um den Mittelpunkt der Alternativen herum gesucht; ein „|“ trennt dagegen mehrere
+    voneinander unabhängige Suchen. Mit „+“ und „-“ lässt sich darüber hinaus im Vektorraum
+    rechnen: <span class="mono">König - Mann + Frau</span> sucht die Nachbarn der Position
+    vec(König) - vec(Mann) + vec(Frau) statt der Position eines einzelnen Wortes. Ein Vorzeichen
+    ist nur am Anfang eines Tokens ein Operator, Bindestrichkomposita wie
+    <span class="mono">Nord-Süd-Dialog</span> bleiben also suchbar.
+</p>
+<p>
+    Die syntagmatische Ansicht rechnet mit. Der prädiktive Kollokationswert eines Kandidaten ist
+    \(\sigma(q \cdot u)\), vor der Sigmoidfunktion also linear in \(q\); ein Ausdruck liefert
+    deshalb die Kontexte, die die berechnete Position vorhersagt – bei „König - Mann + Frau“ die,
+    die König und Frau vorhersagen, Mann aber nicht. Gemittelt wird dabei über die positiven
+    Terme statt zu summieren, damit die Werte in demselben Bereich bleiben wie bei einer
+    einzelnen Wortform: Der informative Bereich der Sigmoidfunktion ist schmal, und die
+    stärksten Kollokatoren eines einzelnen Wortes liegen bereits an seinem oberen Rand. Eine
+    ausgeglichene Analogie (+1 -1 +1) hat einen Term und damit denselben Maßstab wie eine
+    einzelne Wortform.
+</p>
+<p>
+    Die zählbasierten Kollokatoren bleiben dagegen auf eine einzelne Wortform beschränkt: Sie
+    werden pro Knoten in der Kookkurrenzdatenbank nachgeschlagen und lassen sich nicht aus dem
+    Suchvektor berechnen. Operanden, die nicht im Vokabular stehen, werden über dem Ergebnis
+    genannt und bei der Berechnung weggelassen.
+</p>
+
 <h3>Effektive Fenstergröße und Auto-Focus</h3>
 <p>
     Die Assoziationsmaße LL, MI, MI², MI³ und nPMI werden nicht über das gesamte Kontextfenster
@@ -42,6 +70,11 @@
 </p>
 <h3>Änderungen</h3>
 <p>
+    <strong>06.09.2026</strong>
+
+        Das Suchfeld versteht jetzt Vektorarithmetik, siehe <em>Suchanfragen</em> oben.
+</p>
+<p>
     <strong>04.09.2026</strong>
 
         Log-Dice (LD) wird jetzt genau so berechnet, wie es Rychlý (2008) definiert,
diff --git a/templates/en/about.html.ep b/templates/en/about.html.ep
index 20c0ecc..039c427 100644
--- a/templates/en/about.html.ep
+++ b/templates/en/about.html.ep
@@ -9,6 +9,33 @@
     The models used here are based on an extension of word2vec (Mikolov et al. 2013), wang2vec (Ling et al. 2015) 
     and on the other hand on simple co-occurence counts and analysis methods that operate on these.
 </p>
+<h3>Queries</h3>
+<p>
+    Several word forms separated by blanks are added into one query vector, i.e. the search is
+    around the centre of the alternatives, while a &ldquo;|&rdquo; separates several independent
+    searches. Beyond that, &ldquo;+&rdquo; and &ldquo;-&rdquo; do arithmetic in the vector space:
+    <span class="mono">König - Mann + Frau</span> searches the neighbours of the position
+    vec(König) - vec(Mann) + vec(Frau) rather than the position of a single word. A sign is an
+    operator only at the beginning of a token, so hyphenated words such as
+    <span class="mono">Nord-Süd-Dialog</span> remain searchable.
+</p>
+<p>
+    The syntagmatic view follows along. The predictive score of a candidate is
+    \(\sigma(q \cdot u)\), which is linear in \(q\) before the sigmoid, so an expression
+    yields the contexts that the computed position predicts &ndash; for &ldquo;König - Mann +
+    Frau&rdquo; the ones König and Frau predict but Mann does not. The positive terms are
+    averaged rather than summed, so that the values stay in the range a single word form
+    occupies: the sigmoid is informative over a narrow range only, and the strongest collocates
+    of a single word already sit at the top of it. A balanced analogy (+1 -1 +1) is one term and
+    is therefore on the same scale as a single word form.
+</p>
+<p>
+    The count based collocators, in contrast, remain restricted to a single word form: they are
+    looked up per node in the co-occurrence database and cannot be computed from the query
+    vector. Operands that are not in the vocabulary are named above the result and left out of
+    the computation.
+</p>
+
 <h3>Effective window size and auto focus</h3>
 <p>
     The association measures LL, MI, MI², MI³ and nPMI are not computed over the whole context
@@ -40,6 +67,11 @@
 </p>
 <h3>Changes</h3>
 <p>
+    <strong>2026-09-06</strong>
+
+        The search field understands vector arithmetic, see <em>Queries</em> above.
+</p>
+<p>
     <strong>2026-09-04</strong>
 
         Log-Dice (LD) is now computed exactly as defined by Rychlý (2008),
diff --git a/templates/index.html.ep b/templates/index.html.ep
index 9322028..ce38536 100644
--- a/templates/index.html.ep
+++ b/templates/index.html.ep
@@ -2,6 +2,13 @@
 <html>
   <head>
 		<% my $plain_title = $title; $plain_title=~s/<[^>]+>//g; %>
+%# Whether the query was answered at all: not found, and an expression whose
+%# operands cancel each other out, both leave the first list empty.
+% my $have_results = ($lists && @$lists > 0 && $lists->[0] && @{$lists->[0]} > 0);
+%# The count based collocators come out of the co-occurrence database, which is
+%# keyed by one node word, so they have no answer for a query of several
+%# operands. The predictive ones do, see getCollocators().
+% my $single_word = ($operands == 1);
     <title><%= $plain_title  %>:<%= $word %> · IDS word vector analysis</title>
 %# Result pages are computed for one word each and there is one for every
 %# word of the vocabulary, so they are not something to index or to follow.
@@ -44,8 +51,18 @@
      });     
      var urlParams = new URLSearchParams(window.location.search);
      var currentWords = urlParams.get("word");
-     var CIIsearchWords = (currentWords && (currentWords.includes(" ") || currentWords.includes("|")) ? '('+currentWords.replace(/[ |]+/g, " oder ")+')' : currentWords);
+     % use Mojo::ByteStream 'b';
+     // The vocabulary entries the query vector was built from, as the server
+     // resolved them. A query can be a vector expression, "König - Mann +
+     // Frau", and the subtracted operands are deliberately not in here: they
+     // are not marked in the maps, and not part of the KorAP queries built
+     // from the result.
+     var searchedWords = <%= b(Mojo::JSON::to_json($added // '')) %>;
+     var targetWords = " " + searchedWords + " ";
+     var CIIsearchWords = (searchedWords.includes(" ") ? '('+searchedWords.replace(/\s+/g, " oder ")+')' : searchedWords);
      var collocatorTable = null;
+     var classicCollocatorTable = null;
+     var singleWord = <%= $single_word ? 'true' : 'false' %>;
      var plainTitle ="<%= $plain_title %>"  
      var korapPath="/";
      if (plainTitle.match(/-en/)) {
@@ -105,8 +122,8 @@
        var collocatorTable_activated = false;
        $( "#tabs" ).on( "tabsactivate", function( event, ui ) {
          if (localStorage) localStorage['tab'] = ui.newTab.index();
-         if(ui.newTab.index() == 3 && !collocatorTable_activated) {
-           classicCollocatorTable.columns.adjust();
+         if(ui.newTab.index() == 3 && !collocatorTable_activated && collocatorTable) {
+           if (classicCollocatorTable) classicCollocatorTable.columns.adjust();
            collocatorTable.columns.adjust();
            collocatorTable_activated = true;
          }
@@ -143,10 +160,9 @@
          return changeCharColor(str, heat, word);
        }
 
-       % use Mojo::ByteStream 'b';
        var paraResults = <%= b(Mojo::JSON::to_json($lists)) %>;
        var urlprefix =  new URLSearchParams(window.location.search);
-       if (paraResults.length > 0  && paraResults[0] != null) {
+       if (paraResults.length > 0 && paraResults[0] != null && paraResults[0].length > 0) {
          var nvecs = [],
              nwords = [],
              nranks = [],
@@ -157,7 +173,7 @@
            nranks = nranks.concat(paraResults[i].map(function(a){return a.rank;}));
            nmarked = nmarked.concat(paraResults[i].map(function(a){return a.marked;}));
          }
-         showMap({target: " "+urlParams.get('word')+" ", mergedEnd: <%= $mergedEnd %>, words: nwords, vecs: nvecs, ranks: nranks, marked: nmarked} );
+         showMap({target: targetWords, mergedEnd: <%= $mergedEnd %>, words: nwords, vecs: nvecs, ranks: nranks, marked: nmarked} );
          var t = $('#firsttable').DataTable({
            data: [].concat.apply([], paraResults),
            "sScrollY": "780px",
@@ -311,19 +327,24 @@
          var filterQuot = /^quot/;
          var ccResult;
          var baseURL =  window.location.pathname.replace(/[/]$/, '')
-         classicCollocatorTable = makeClassicCollocatorTable('#classicoloctable', baseURL, paraResults[0][0].rank)
+         // Only for a one word query: the node of a count based profile is a
+         // word, and paraResults[0][0] is the nearest word to the query
+         // vector, which is not what was asked for.
+         if (singleWord) {
+           classicCollocatorTable = makeClassicCollocatorTable('#classicoloctable', baseURL, paraResults[0][0].rank)
 
-         $('#show-details').change(function (e) {
-           var columns = classicCollocatorTable.columns(".detail");
-           if(this.checked) {
-             columns.visible(true);
-             $("#ccd").css('width', 'auto');
-           } else {
-             columns.visible(false);
-             $("#ccd").css('width', '680px');
-           }
-           classicCollocatorTable.columns.adjust().draw();
-         } );
+           $('#show-details').change(function (e) {
+             var columns = classicCollocatorTable.columns(".detail");
+             if(this.checked) {
+               columns.visible(true);
+               $("#ccd").css('width', 'auto');
+             } else {
+               columns.visible(false);
+               $("#ccd").css('width', '680px');
+             }
+             classicCollocatorTable.columns.adjust().draw();
+           } );
+         }
 
          $("td.collocator").click(function(){
            queryKorAPCII(this.textContent + " /w1:5,s0 " + CIIsearchWords);
@@ -694,7 +715,7 @@
          $.post(baseURL+'/getVecsByRanks',
                 JSON.stringify(nranks),
                 function(data, status){
-                  showMap({target: " "+urlParams.get('word')+" ", mergedEnd: <%= $mergedEnd %>, words: nwords, vecs: data, ranks: nranks, marked: Array(100).fill(false)} );
+                  showMap({target: targetWords, mergedEnd: <%= $mergedEnd %>, words: nwords, vecs: data, ranks: nranks, marked: Array(100).fill(false)} );
                 }, 'json');
        }
      }
@@ -771,6 +792,12 @@
         </div>
       </div>
     </div>
+    %# Operands that are not in the vocabulary are dropped from the query
+    %# vector, which for an expression like "König - Mannn + Frau" would
+    %# otherwise silently answer a different question.
+    % if($unknown ne '' && $have_results) {
+      <div id="unknownwords"><%= loc 'not_in_vocabulary' %> <span class="mono"><%= $unknown %></span></div>
+    % }
     <div id="topwrapper">
       <div style="visibility: hidden;" id="tabs">
         <ul>
@@ -780,7 +807,11 @@
             % }
             <li><a href="#tabs-1"><%= loc 'paradigmatic_tsne' %></a></li>
             <li><a href="#tabs-2"><%= loc 'paradigmatic_som' %></a></li>
-            <li><a href="#tabs-3"><%= loc 'syntagmatic' %></a></li>
+            %# No syntagmatic tab for a model without a .net file, i.e. without
+            %# the output weights the predictive collocators are read from.
+            % if($collocators) {
+              <li><a href="#tabs-3"><%= loc 'syntagmatic' %></a></li>
+            % }
           % }
           <li><a href="#tabs-4">Info</a></li>
         </ul>
@@ -807,7 +838,7 @@
         </div>
         % }
         <div id="tabs-1" style="display: flex;  padding: 5px; flex-flow: row wrap;">
-          % if($lists && (@$lists) > 0 && (@$lists)[0]) {
+          % if($have_results) {
             <div id="wrapper">
               <div id="first" style="width: 230px; margin-bottom: 15px;">
                 <table class="display compact nowrap" id="firsttable">
@@ -893,6 +924,7 @@
             </div>
           % }
         </div>
+        % if($collocators) {
         <div id="tabs-3" style="display: flex;  padding:5px; flex-flow: row wrap;">
           <div style="margin-right: 20px; margin-bottom: 10px;" id="secondt">
             <table class="display compact nowrap"  id="secondtable">
@@ -928,6 +960,9 @@
               </tbody>
             </table>
           </div>
+          % if(!$single_word) {
+            <div id="ccd" class="notice"><%= loc 'ca_single_word_only' %></div>
+          % } else {
           <div id="ccd" style="">
             <table class="display compact nowrap" id="classicoloctable">
               <thead>
@@ -973,11 +1008,13 @@
               </tbody>
             </table>
           </div>
+          % }
           <!--
                <div style="clear:both" ></div>
                <div style="float: right; overflow: hidden" id="extra"><button onClick="showCollocatorSOM()"> </button></div>
           -->
         </div>
+        % }
         <div id="tabs-4" style="display: flex;  padding:5px; flex-flow: row wrap;">
           <div id="info">
             <h3><%== loc 'about' %></h3>