A bookcase may be fitted with glass doors that can be closed to protect the books from dust or moisture. Bookcase doors are almost always glazed with glass, so as to allow the spines of the books to be read. Especially valuable rare books may be kept in locked cases with wooden or glazed doors. A small bookshelf may also stand on some other piece of furniture such as a desk or chest. Larger books are more likely to be kept in horizontal piles and very large books flat on wide shelves or on coffee tables.
In Latin and Greek the idea of bookcase is represented by Bibliotheca and Bibliothēkē (Greek: βιβλιοθήκη), derivatives of which mean library in many modern languages. A bookcase is also known as a bookshelf, a bookstand, a cupboard and a bookrack. In a library, large bookshelves are called "stacks."