Uncertainty (knowledge representation) is a concept studied within the fields of experimental psychology and knowledge representation, referring to the formal or psychological methods used to encode, represent, and manage information that is incomplete, imprecise, unreliable, or probabilistic within a knowledge system or cognitive model. It investigates the mechanisms by which agents (human or artificial) handle degrees of belief, vagueness, ambiguity, or missing data during reasoning, inference, and decision-making processes. The significance of this concept lies in its crucial role in developing robust systems and understanding cognitive processes that operate effectively despite the inherent imperfections and partial nature of real-world knowledge.