Any situation in which the current state of knowledge is such that:

  1. the order or nature of things is unknown, 
  2. the consequences, extent, or magnitude of circumstances, conditions, or events is unpredictable, and 
  3. credible probabilities to possible outcomes cannot be assigned. 

Uncertainty can result from lack of information or from disagreement about what is known or even knowable. Uncertainty can be represented by quantitative measures (e.g., a range of values calculated by various models) or by qualitative statements (e.g., reflecting the judgment of a team of experts).