tail bone vs spine

tail bone and spine both are nouns.

Word	Noun	Adjective	Verb	Adverb
tail bone	Yes	No	No	No
spine	Yes	No	No	No

tail bone (noun)	spine (noun)
the end of the vertebral column in humans and tailless apes	a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin
	the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved
	the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
	a small sharp-pointed tip resembling a spike on a stem or leaf
	any sharply pointed projection