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Phase diagram

A phase diagram or phase space is a useful construct used in mathematics and physics to demonstrate and visualise the changes in a given system.

Every degree of freedom or parameter of the system is represented as an axis of a multidimensional space. Time is not considered to be one of the dimensions but rather is allowed to flow letting the system (which is represented as a single point moving through the phase space) evolve. A phase space may contain very many dimensions, For instance a gas containing many molecules may require a separate dimension for each particle's x, y and z positions and velocities as well as any number of other properties.

See also Hamiltonian mechanics.