This idea comes up particularly in the phase space coordinate of Hamiltonian mechanics.
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Phase space has one position coordinate and one conjugate momentum for every degree of freedom; a point specifies an instantaneous mechanical state.
Phase space is a concept used in physics and mathematics to represent the state of a dynamic system. It is particularly useful in the fields of classical mechanics, statistical mechanics, and quantum mechanics. In phase space, each possible state of a system is represented by a point, with dimensions corresponding to the degrees of freedom of the system.