How can I delete the word `Category:` from page titles? [duplicate]

For achieve this title you need to extend get_the_archive_title . here is how or check the official doc

function wpse64458_get_the_archive_title($title){
    if ( is_category() ) {
        $title = single_cat_title( '', false );
    } elseif ( is_tag() ) {
        $title = single_tag_title( '', false );
    }
    return $title;
}
add_filter( 'get_the_archive_title', 'wpse64458_get_the_archive_title');