In matrix mechanics, the mathematical formulation of quantum mechanics, any pair of non- commuting self-adjoint operators representing observables are subject to similar uncertainty limits. An eigenstate of an observable represents the state of the wavefunction for a certain measurement value (the eigenvalue). For example, if a measurement of an observable A is performed, then the system is in a particular eigenstate Ψ of that observable. However, the particular eigenstate of the observable A need not be an eigenstate of another observable B : If so, then it does not have a unique associated measurement for it, as the system is not in an eigenstate of that observable.