The term gnosiology (μελετώ του γνώση ) is derived from the Greek words gnosis ('knowledge', γνώση) and logos ('word' or 'discourse', λέξη). Linguistically, one might compare epistemology, which is derived from the Greek words episteme ('knowledge') and logos (for a discussion of the exact meaning of gnosis in Ancient Greek, see the Gnosticism article). As a philosophical concept, gnosiology broadly means the theory of knowledge, which in ancient Greek philosophy was perceived as a combination of sensory perception and intellect. When considered in the context of science, gnosiology takes on a different meaning: the study of knowledge, its origin, processes, and validity.