be defined with the <code class="mendoza-code">defn</code> macro, like so:
</p>
<pre class="mendoza-codeblock"><code data-language="janet">(<span class="mdzsyn-coresym">defn</span> <span class="mdzsyn-symbol">triangle-area</span>
 <span class="mdzsyn-string">"Calculates the area of a triangle."</span>
 [<span class="mdzsyn-symbol">base</span> <span class="mdzsyn-symbol">height</span>]
 (<span class="mdzsyn-coresym">print</span> <span class="mdzsyn-string">"calculating area of a triangle..."</span>)
 (<span 