In economics, the term profit has two related but distinct meanings. Normal profit represents the total opportunity costs (both explicit and implicit) of a venture to an investor or entrepreneur, whilst economic profit (also abnormal, pure, supernormal or excess profit, as the case may be monopoly or oligopoly profit, or simply profit) is, at least in the neoclassical microeconomic theory which dominates modern economics, the difference between a firm's total revenue and all costs, including normal profit. Economic profit is thus contrasted with economic interest which is the return to an owner of capital stock or money or bonds. A related concept, sometimes considered synonymous in certain contexts, is that of economic rent - economic profit can be considered as entrepreneurial rent. Economic profit in contemporary neoclassical economics should be differentiated from that of the previously dominant school of classical economics and Marxian economics, which defined profit as the return to the employer of capital stock (such as machinery, factories, and ploughs) in any productive pursuit involving labor.