In political economy and especially Marxian economics, exchange value (German: Tauschwert) refers to one of the four major attributes of a commodity, i.e., an item or service produced for, and sold on the market, the other three attributes being use value, economic value, and price. Thus, a commodity has the following: a value, represented by the socially necessary labour time to produce it (Note: the first link is to a non-Marxian definition of value); a use value (or utility); an exchange value, which is the proportion at which a commodity can be exchanged for other entities; a price (an actual selling price, or an imputed ideal price). These four concepts have a very long history in human thought, from Aristotle to David Ricardo, and became more clearly distinguished as the development of commercial trade progressed but have largely disappeared as four distinct concepts in modern economics. This entry focuses on Marx's summation of the results of economic thought about exchange value. Exchange value and price according to Marx Marx regards exchange-value as the proportion in which one commodity is exchanged for other commodities. For Marx, exchange-value is not identical to the money price of a commodity. Actual money prices (or even equilibrium prices) will only ever roughly correspond to exchange-values. The relationship between exchange-value and price is analogous to the relationship between the exact measured temperature of a room and the everyday awareness of that temperature from feeling alone. Thus, Marx did not regard divergence between the two as a refutation of his theory. The value of a good is determined by the socially necessary labour time required to produce the commodity. Marx believed that an understanding of exchange-value was necessary to explain fluctuations in price. Exchange-value does not need to be expressed in money-prices necessarily (for example, such as in countertrade: x amount of goods p are worth y amounts of goods q). Marx makes this abundantly clear in his dialectical derivation of the forms of value in the first chapters of Das Kapital (see value-form). It was only in the 13th century AD when the word "price" came into use in Western Europe, its Latin root being "pretium", meaning "reward, prize, value, worth", referring back to the notion of "recompense", or what was given in return, the expense, wager or cost incurred when a good changed hands. Its verb meaning "to set the price of" was used only