Other forms: bookshelves
A bookshelf is the piece of furniture your books stand in rows on. One board, or several in a frame.
Strictly a bookshelf is a single shelf and a bookcase is the whole thing, though almost nobody keeps the distinction. The plural is bookshelves. It has become a way of describing a person, since what somebody keeps on their bookshelf is treated as evidence about them, and the bookshelf behind a head in a video call has been analysed more than any furniture deserves.
1nounbookshelfA shelf or set of shelves for holding books.
“The bookshelf sagged in the middle.”
Also accepted in games: bookcase
From book + shelf.
Etymology from Wiktionary, CC BY-SA