In science, a process that isn't reversible is called irreversible. This concept arises most frequently in thermodynamics, as applied to processes. Irreversibility is also used in economics to refer to investment or expenditures that involve large sunk costs. From a thermodynamics perspective, all natural processes are irreversible. The phenomenon of irreversibility results from the fact that if a thermodynamic system of interacting molecules is brought from one thermodynamic state to another, t… (More on Irreversibility)