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This plugin enables you to define groups for tags (or categories) and then assign tags (or categories) to them. The group membership is saved in the native WP table field term_group, so it won’t create additional tables in the database. The plugin comes with a configurable tag cloud where tags are displayed in tabs sorted by groups.

Possible applications are:

• Display your tags grouped by language or by topic.
• Display your tags in any order, independently from their names or slugs.
• Choose which tags to display in different sections of your blog.

Please find more information here.