Q. Definition of Money?
Before talking over macroeconomic models we should define what we mean by money. Money has aninteresting and long history and an understanding of how we came to use money is useful for any macroeconomist. Unfortunately, there isn't enough space to explain how money was 'invented' and how it evolved over time. There are, though, many excellent descriptions on Internet.
'Money' in economics is in fact not as simple to understand as you may think and many use the term money in a way inconsistent with how it's described in economics. Money is defined as any token or commodity which is generally accepted as payment of goods and services.