I
In economics, equality in price, rate of exchange, purchasing power, or wages.
In international exchange, parity exists when the exchange rate between two supply and demand , or through the intervention of national governments or international agencies such as the International Monetary Fund . In U.S. agricultural economics, the term parity is used for a system of regulating the prices of farm commodities, usually by government price supports and production quotas, to guarantee farmers the purchasing power they had in a past base period. Parity is also used in personnel administration to establish equitable wage rates for various classes of employees.
II
In physics, a property related to the symmetry of the {{link=wave function">wave function representing a system of fundamental particles.
It plays an important role in quantum mechanics in the description of a physical system. Parity transformation replaces a system with a type of mirror image in which the spatial coordinates describing the system are inverted, so that the coordinates x , y , and z are replaced with - x , - y , and - z . If a system is identical to the original system after parity transformation, its parity is even. If the image is the negative of the original, its parity is odd. In either case, the physical observables of the system remain unchanged. In 1957 Chien-Shiung Wu (1912–1997) and coworkers made the surprising discovery that beta decay reactions do not conserve parity; in other words, the inverted image of the process does not exist in nature. This is a general property of the weak force .