In [[quantum mechanics]], '''conjugate quantities''' are a pair of observable quantities whose associated [[operators]] do not commute.
Conjugate quantities are linked by the [[Heisenberg uncertainty principle]]. The best-known example is the pair of observables [[Position operator|position]] and [[Momentum operator|momentum]].
The Uncertainty principle follows from the mathematical description of the conjugate quantities as operators; it is then a theorem of [[functional analysis]].
