back (body part) book spine 3 realizations
ACCEPTED Realization 1
type Polysemy
language English
lexeme back
meaning 1 rear of the body, especially the part between the neck and the end of the spine and opposite the chest and belly
direction
meaning 2 book spine

    The titles are printed on the backs of the books.

reference OED
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ACCEPTED Realization 2
type Polysemy
language English
lexeme spine
meaning 1 series of bones situated at the back from the head to the pelvis of a human, or from the head to the tail of an animal, enclosing the spinal cord and providing support for the thorax and abdomen
direction
meaning 2 narrow, bound edge of a book that encloses the inner edges of the pages, facing outwards when the book is on a shelf and typically bearing the title and the author's and publisher's name

The spine is the book's backbone. Because the spine is generally all you can see when a book is on the shelf, the spine displays the title and author of the book and is often ornately decorated.

(“Rare Book Basics: Book Terms Illustrated”, in Powell's City of Books http://web.archive.org/web/20140705063024/http://www.powells.com/rarebooks/bookbasics.html )

reference OED
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ACCEPTED Realization 3
type Polysemy
language French
lexeme dos
meaning 1 back (body part)
direction
meaning 2 book back
reference <personally collected data>
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