Epistemology—This term comes from the Greek epistme (knowledge) and lgos (the study of). Epistemology is one of the four main branches of philosophy (besides ethics, logic and metaphysics). It asks questions regarding knowledge: What is knowledge? Where does it come from? How is it formulated, expressed and communicated? Is sense experience necessary for all types of knowledge? What part does reason play in knowledge? Is there knowledge derived only from reason? What is the difference between belief, knowledge, opinion, fact, reality, error, imagining, conceptualization, idea, truth, possibility and certainty? See Ethics, Logic, Metaphysics, Ontology, Philosophy.