Fish bone is any bone of a fish. Fish bone also includes the bony, delicate parts of the skeleton of bony fish, such as ribs and fin rays, but especially the ossification of connective tissue lying transversely inclined backwards to the ribs between the muscle segments and having no contact with the spine.
Not all fish have fish bones in this sense; for instance, eels and anglerfish do not.
There are several series of fish bones: Epineuralia, Epicentralia, Epipleuralia and Myorhabdoi.