Money is a resource with a set of characteristics that are embodied in different combinations in monetary assets (forms of money). The main characteristics of money are: trustworthiness, divisibility, maintenance of value over location & time, limitation of supply, and convenience. These characteristics allow money to be used in accounting and recording of transactions & wealth; and forms of money to be used as mediums of exchange and savings. Monetary assets include notes & coin, bank loans/deposits, credit & debit cards, and various government-backed and short-term bills of exchange.
Since commercial banks can generate loans if consumers or firms request them, the supply on money is endogenous to the monetary system.
Barker, Terry ‘Endogenous money in 21 Century Keynesian economics’, chapter 6, pp. 202-239 in Philip Arestis and Malcolm Sawyer (eds) 21 Century Keynesian Economics, Palgrave Macmillan, 2010.
Fontana G. 2009. Money, Uncertainty and Time. Psychology Press
Skidelski, Robert (2018) Money and Government: A Challenge to Mainstream Economics, Allen Lane, London.