Uncertainty refers to a lack of certainty or knowledge about something. It is an unclear, unknown, or ambiguous state in which information is not available or there is doubt and confusion about what might happen next. Uncertainty can be caused by various factors such as incomplete data, conflicting evidence, unpredictable events, or simply the nature of complex systems that are difficult to understand or predict. It is often associated with risk, danger, or fear because it involves unknown outcomes and potential negative consequences.