Bookplates, also known as ex libris, are labels or tags placed inside books to indicate ownership. There are several synonyms for the word 'bookplates.' Firstly, the term 'book labels' is often used to refer to the same item. Another synonym is 'book ownership inscriptions.' This refers to handwritten notes or inscriptions inside books that indicate a book's owner. 'Book stamp' is another synonym and is used when a personalized rubber stamp is used to mark ownership. Finally, the term 'book adornments' can be used when discussing decorative bookplates or labels that are made of beautiful designs and are used to enhance the appearance of a book.