What is the difference between stock and broth?

Stock and broth are foundational in cooking. From soups and stews to a cooking medium for everything from grains to vegetables, to the basis of sauces and gravies, it is no wonder that many recipes begin with stock or broth in their ingredient list. The two are used nearly interchangeably in print, and in fact, many recipes will call for stock OR broth, which raises the question. What exactly is the difference between stock and broth?