This section clarifies the concept of capital by distinguishing it from any isolated material form (money, means of production, or commodities). Capital should be understood primarily as a historically specific social relation mediated by things—namely, a relation through which value is systematically expanded under determinate conditions of production and exchange. On this basis, the section draws a strict distinction between money functioning as “pure money” and money functioning as capital, and locates the difference in the form of circulation: from selling in order to buy (C–M–C) to buying in order to sell (M–C–M’). It further differentiates three major forms of capital—interest-bearing capital, commercial capital, and industrial capital—and argues that the first two may arise on the basis of commodity circulation alone, often exerting external pressure on production. By contrast, industrial capital presupposes the emergence of “free” wage labor and the separation of direct producers from their means of production. Where industrial capital becomes dominant, commercial capital and interest-bearing capital are transformed and subordinated to the requirements of production (e.g., commercial capital becomes a functional moment of circulation, and usury tends to develop into banking capital). Where this transformation fails, pre-capitalist forms—independent commercial capital and usurious finance—retain predominance and may obstruct the development of industrial capital.