What is a system?

That is a tough question because so much can be a system. It is better for now to ask what is not a system.

What is not a system?

A thing.

Are two things a system?

No. The number of things has little to do with a system.

Are many things a system?

No, a big pile of things is the same as a small pile of things.

Well, if one thing is not a system, and if two things are not a system, and if many things is not a system, what else is there?

The relationship between things.

Isn't their relatinship a thing?

No. A relationship is what something is doing to something else.

Is a sysstem a relationship between things?

Yes.