What precisly is a bone?

A lot on people talk about Poser bones. I spend a lot of time messing around inside Poser libeary files, but have never seen anything named "bone" in any one of them. Of couse I know that it has something to do with the Setup Room (which I never use), and those triangular icins.

But what in precise technical terms is a bone? Is it the entire actor in all sections of the cr2; morphs, crease angle, 'addChild' stuff, weld statement, geometry assignment,  the whole kit and cboodle? Or is it some subset of the above, and if a subset, what exactly is included in, or excluded from the subset?

I have wondered about this for a long time. I've been kind of embarrised to ask. I assumed that one day the meaning would become clear to me, but it never has. So please, your best stab at a precise technical definition of the word "bone".

Quote - But what in precise technical terms is a bone?

It's a named element of a the skeleton hieracrchy.
It has a start point, an end point, a name, and a transformation relative to it's parent.  

Quote - Is it the entire actor in all sections of the cr2; morphs, crease angle, 'addChild' stuff, weld statement, geometry assignment,  the whole kit and caboodle?

Everything else is part of the actor with which the bone is associated.

To add an aside to that - Poser's concept of a bone is really nothing more than a means of picturing the joint centres and the hierarchical relationships when using the setup room. I don't recall the term being used before Pro Pack (the first version with a setup room included) was released. As such, it only goes part of the way way towards describing what happens when a joint bends. As nruddock says, the rest of the important stuff is covered by the concept of the actor.

I understand that other 3D application's rigs have a more comprehensive skeleton, but I know nothing about them so should probably avoid saying any more. ;) 

Thank you for the explaination. I appreciate them :)