I deleted a book, but its subject (or author, etc.) remains in KyBook 3 even though no other book is using it.

Because metadata entries can be added manually by the user as well as automatically by KyBook 3, there is no way of telling what the user's intentions are for unused items.

For this reason, there is an option to delete an unused item in the Cataloguer screens. For example, to delete an unused subject:

1. Tap the Cataloguer icon on the Library (home) screen
2. Tap Subjects
3. Tap the Command icon at the top right of the screen
4. Tap Delete empty