In trade, barter is a system of exchange in which participants in a transaction directly exchange goods or services for other goods or services without using a medium of exchange, such as money. Economists usually distinguish barter from gift economies in many ways; barter, for example, features immediate reciprocal exchange, not one delayed in time. Barter usually takes place on a bilateral basis, but may be multilateral. In most developed countries, barter usually exists parallel to monetary systems only to a very limited extent. Market actors use barter as a replacement for money as the method of exchange in times of monetary crisis, such as when currency becomes unstable or simply unavailable for conducting commerce.