Capital
In economics, capital goods or capital are "those durable produced goods that are used as productive inputs for further production" of goods and services. At the macroeconomic level, "the nation's capital stock includes buildings, equipment, software, and inventories during a given year" [Samuelson, Nordhaus, p. 442].
A typical example is the machinery used in factories. Capital can be increased by using the factors of production, which excludes certain durable goods like homes and personal automobiles that are not used in the production of saleable goods and services.
Adam Smith defined capital as "that part of man's stock which he expects to afford him revenue." In economic models, capital is an input in the production function. The total physical capital at any given moment in time is referred to as the capital stock (not to be confused with the capital stock of a business entity). Capital goods, real capital, or capital assets are already-produced, durable goods or any non-financial asset used in producing goods or services.
In Marxian critique of political economy, capital is reproduced by social relations and could not exist without labor. Karl Marx himself stated it: "Capital is dead labor, that, vampire-like, only lives by sucking living labor, and lives the more, the more labor it sucks" [Marx, p.66].
Marx Karl. (1971). Grunddragen i kritiken av den politiska ekonomin. Lund: Zenit.
Samuelson Paul A., Nordhaus William D. (2001). Economics 19th Edition. New York: McGraw-Hill.