The definition of currency is a system of money in general use in a particular country.
Does system in this context means definition #11 from Google definition?
sys·tem noun /ˈsistəm/ systems, plural
A set of connected things or parts forming a complex whole, in particular
A set of things working together as parts of a mechanism or an interconnecting network -the state railroad system -fluid is pushed through a system of pipes or channels
- A set of organs in the body with a common structure or function -the digestive system
- The human or animal body as a whole - you need to get the cholesterol out of your system
- A group of related hardware units or programs or both, esp. when dedicated to a single application
- (in chronostratigraphy) A major range of strata that corresponds to a period in time, subdivided into series
- A group of celestial objects connected by their mutual attractive forces, esp. moving in orbits about a center -the system of bright stars known as the Gould Belt
- A set of principles or procedures according to which something is done; an organized scheme or method -a multiparty system of government -the public school system
- Orderliness; method -there was no system at all in the company
- A method of choosing one's procedure in gambling
- A set of rules used in measurement or classification -the metric system
- The prevailing political or social order, esp. when regarded as oppressive and intransigent -don't try bucking the system
- A set of staves in a musical score joined by a brace