In english, we might talk about the relation between, say, Bob and Tim. Perhaps they're cousins. The term "relation" in this context makes sense to me.

In the context of relational databases, I understand what the term refers to, but I don't understand why it is used. I figure that understanding why it is used will help me to better understand the field, so I'd like to understand why it is used.

* Why is, for example, a Person, considered to be a "relation"? In english, a relation is a noun that describes how two entities are associated. It doesn't refer to the entities themselves. In the context of relational databases, "relation" refers to the entities themselves. Why?
* I understand that relational model came after the hierarchical and network models (ex. parent, neighbor). But in those models, the entities also have relations to one another. So why call this model the relational model? Is there a more specific phrase/term? Or maybe we should say that all three models are relational models, but the hierarchical and network models are specific types of relational models?
* What if we have standalone entities that don't relate to one another. Say, Person, Door, and Tree. Is the term "relation(al)" still applicable?

(Perhaps this should be multiple questions. I figured that the answers are highly related - perhaps there's just one answer - so I figured it'd make sense for this to be a single question. If I'm wrong, let me know and I'll create separate questions instead.)

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Edit: This diagram may be useful to visualize that a relation is relating different domains to one another:

[![enter image description here](https://i.stack.imgur.com/u6hAQ.png)](https://i.stack.imgur.com/u6hAQ.png)