<p>The purpose of a Wiki excerpt is <em>not</em> to supply as full and complete a definition as you can.  <em>It is to help people apply tags appropriately</em>.  To be effective, the excerpt therefore should:</p>

<ul>
<li><p>Be as short as possible, for otherwise it will be ignored.</p></li>
<li><p>Be clear about what the tag means--but only to the point of distinguishing it from other possible tags that could reasonably be applied.</p></li>
<li><p>Distinguish it from related tags.</p></li>
<li><p>Provide guidance concerning how the tag is intended to be used (or not used).</p></li>
</ul>

<p>For some of the more effective examples, read the excerpts for the <a href="https://stats.stackexchange.com/questions/tagged/r" class="post-tag" title="show questions tagged &#39;r&#39;" rel="tag">r</a>, <a href="https://stats.stackexchange.com/questions/tagged/self-study" class="post-tag" title="show questions tagged &#39;self-study&#39;" rel="tag">self-study</a>, and <a href="https://stats.stackexchange.com/questions/tagged/clustering" class="post-tag" title="show questions tagged &#39;clustering&#39;" rel="tag">clustering</a> tags.  (To fully appreciate how those excerpts will appear, you will need to find a page on the main site that displays a tag--which can be done by clicking through the links in the preceding sentence--and hovering your mouse over the tag wherever it appears.)</p>

<p>I warmly encourage qualified community members to review tags in subjects you are interested in, to create or modify their excerpts to meet these objectives, and--if you are so inspired--to supply additional information in the tag wiki itself.  If you want to write a review of a subject, though, then please consider our blog page: it's a much better alternative.</p>
