A bookcase, or bookshelf, is a piece of furniture with horizontal shelves, often in a cabinet, used to store books or other printed materials. Bookcases are used in private homes, public and university libraries, offices, schools, and bookstores. Bookcases range from small, low models the height of a table to high models reaching up to ceiling height. Shelves may be fixed or adjustable to different positions in the case. In rooms entirely devoted to the storage of books, such as libraries, they may be permanently fixed to the walls and/or floor. 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 (), 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." History East Asia Revolving bookcases, known as zhuanlunzang (), have been documented in imperial China, and its invention is credited to Fu Xi in 544. Descriptions of revolving bookcases have been found in 8th- and 9th-century Chinese texts. Revolving bookcases were popularized in Buddhist monasteries during the Song Dynasty under the reign of Emperor Taizu, who ordered the mass printing of the Buddhist Tripiṭaka scriptures. An illustration of a revolving bookcase is depicted in Li Jie's architectural treatise the Yingzao Fashi. Europe Private libraries appeared during the late Roman republic: Seneca inveighed against libraries fitted out for show by illiterate owners who scarcely read their titles in the course of a lifetime, but displayed the scrolls in bookcases (armaria) of citrus wood inlaid with ivory that ran right to the ceiling: "by now, like bathrooms and hot water, a library is got up as standard equipment for a fine house" (domus). When books were written by hand and were not produced in great quantities, they were