Uncertainty (quantum physics) is a fundamental concept asserting that certain pairs of complementary physical properties of a quantum system, such as position and momentum or energy and time, cannot be simultaneously known with arbitrary precision. This principle, notably formulated as the Heisenberg Uncertainty Principle, establishes an inherent, inescapable lower limit on the product of the standard deviations of the measurements of these conjugate variables. It signifies that the act of precisely determining one property necessarily increases the uncertainty in the value of its complementary property, reflecting the intrinsic probabilistic nature of quantum mechanics and fundamentally distinguishing it from classical physics.