A “system” is like a “family”. A family is a system. A family can be a human family or an animal family. It is not important what makes up a family,what is important is that what makes up a family acts like a family. A family is a whole made of the parts of a family. The parts of a family are related. What is important about a family is how we talk about the family. Most of the time we talk about Bill or Jane or Bob. But in a family we talk about mother or father or son So the language of a system is about the relationships within the family. We can also talk about friends or buddies. That way we know what is in the family and what is not.