A string variable containing the text for the link to the next page in the category.
The text displayed is one of either "Next", "Next page" or "Next n photos", depending on what was selected in the Articles Per Page - Next Link menu in the Navigation page of the Settings section.
Example
In the example below, the text for the next page is displayed and linked to the URL for the next page (which is contained within the variable category.next_articles_url).