Subject: What is (if any) the difference between fur, hair, and wool?

In reading about different animals, descriptions often refer to the coat being 
of either fur, hair, or wool using phrases similar to "an outer coat of long 
guard hairs over an undercoat of wool". While I understand what that means and 
how it works for the animal, I wondered if there was any scientific and 
physical difference between the various types.

Re: What is (if any) the difference between fur, hair, and wool?