Different countries have different currencies based on locations, natural resources, and some other aspects. This differences can be barriers between those countries to do trading processes. Moreover, considering the scale of globalisation make the countries need each others. To address this problem, some people say that single world currency is needed to remove the barrier. I disagree with the opinion because that means the money is maintained by one country. This monopoly can benefit certain groups and different exchange rates for each currency can lead to problems.