Uncertainty n. : The quality or state of being uncertain.

Uncertainty n. : That which is uncertain; something unknown.

Example:
How to calculate Uncertainty for rate of reaction?

Taxonomy
uncertainty, risk, measurement, measurement uncertainty, loss, outcome, probabilities, values, possible outcomes, free encyclopedia, risk and uncertainty, standard deviation, EOL, risk neutral, definitions, true value, sigma, loss functions.

Defination from the web:
Uncertainty is a term used in subtly different ways in a number of fields, including philosophy, physics, statistics, economics, finance, ... Main article: Knightian uncertainty ... Uncertainty must be taken in a sense radically distinct from the familiar notion of risk, from which ...