 <p>These are all comments:</p> <pre><code>// // .............. //.............. // ////////////// //////////////// /// /// .............. </code></pre> <p>since the comment extends from the <code>//</code> to the end of the line.</p> <p><strong>Edited to add:</strong> Of course, there are various contexts where neither <code>//</code> nor <code>///</code> introduces a comment. For example:</p> <pre><code>'///' &lt;-- this is a string "///" &lt;-- this is a string (same as previous) /[///]/ &lt;-- this is a regular expression (same as /\//) /* /// */ &lt;-- this is a comment delimited by /*...*/ /\///3 &lt;-- this is /\// divided by 3, i.e., not-a-number </code></pre>