What Is Mono-metallism, Bi-metallism And Fiat Standard?

mono-metallism: When one metal gold or silver is adopted as a standard of value, the system is known as mono-metallism. If the standard metal is gold it is known as gold standard and again if the standard metal is silver it is called the silver standard
Bi-metallism: when both gold and silver freely circulate as legal tender at a fixed ration of exchange with each other and are freely minted the system is known as bi-metallism
Fiat standard:

The fiat standard may be defined as monetary system in which the value or purchasing power of the monetary unit is not kept equal to the value of a specific quantity of a particular metal or a group of metals. Fiat standard may originate in the deliberate issue of medium exchange which have negligible metallic value in themselves, which are not redeemable at a designated ratio in a particular commodity and which have purchasing power independent of that power of any specified commodity.

We may say that fiat standards are more likely to originate when countries which have previously maintained metallic standards suspend the redemption of outstanding mediums of exchange in the monetary metal and at the same time permit their purchasing power to fall below that of the metal in which they were formerly redeemable.

Types of Fiat Standards