Setting the page title for a category page
We would need to know how you render your title. Otherwise it would just be 

&lt;!DOCTYPE html&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml" &gt;
&lt;head&gt;
    &lt;meta charset="utf-8" /&gt;
    &lt;title&gt;{% if title is defined %}{{ title }} {% endif %}{{ siteName }}&lt;/title&gt;
&lt;/head&gt;


and in your category template

{% set title = 'Category ' ~ category.title %}