rds" title="Permalink to this heading">#</a></h1>
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<p class="admonition-title"><span class="caption-number">Definition 5 </span></p>
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<p>If <span class="math notranslate nohighlight">\(x\)</span> and <span class="math notranslate nohighlight">\(y\)</span> are words, then <span class="math notranslate nohighlight">\(x + y\)</span> is the <em>concatenation</em> of <span class="math notranslate