uncertainty principle

American  

noun

Physics.

1. the principle of quantum mechanics, formulated by Heisenberg, that the accurate measurement of one of two related, observable quantities, as position and momentum or energy and time, produces uncertainties in the measurement of the other, such that the product of the uncertainties of both quantities is equal to or greater than h/ 2 π, where h equals Planck's constant.

---

uncertainty principle British  

noun

1. Also known as: Heisenberg uncertainty principle.   indeterminacy principle.  the principle that energy and time or position and momentum of a quantum mechanical system, cannot both be accurately measured simultaneously. The product of their uncertainties is always greater than or of the order of h , where h is the Planck constant

---

uncertainty principle Scientific  

/ ŭn-sûr′tn-tē /

1. A principle, especially as formulated in quantum mechanics, that greater accuracy of measurement for one observable entails less accuracy of measurement for another. For example, it is in principle impossible to measure both the momentum and the position of a particle at the same time with perfect accuracy. Any pair of observables whose operators do not commute have this property. As defined in quantum mechanics, it is also called Heisenberg's uncertainty principle. Similar uncertainty principles hold for non-quantum mechanical systems involving waves as well.

---

uncertainty principle Cultural  

1. The statement in quantum mechanics, formulated by Werner Heisenberg, that it is impossible to measure two properties of a quantum object, such as its position and momentum (or energy and time), simultaneously with infinite precision.

---

Etymology

Origin of uncertainty principle

First recorded in 1930–35

Example Sentences

Simon Stephens’ drama, presented at the Mark Taper Forum in 2017, is a two-hander that tests the validity of the uncertainty principle in the arena of human relationships.

From Los Angeles Times • Dec. 17, 2025

Quantum theory tells us that particles obey Heisenberg's uncertainty principle, and we can never know their position or velocity at the same time.

From Science Daily • Dec. 4, 2023

This is because of an idea in quantum physics called Heisenberg's uncertainty principle.

From Scientific American • Apr. 29, 2023

And putting an observer in an exam room would create the medical version of the uncertainty principle: “Once an observer is in there everyone’s behavior will subtly change,” he said.

From New York Times • Oct. 13, 2022

Using the no boundary condition, we find that the universe must in fact have started off with just the minimum possible non-uniformity allowed by the uncertainty principle.

From "A Brief History of Time: And Other Essays" by Stephen Hawking