When something closely relates to a subject it is called the subject.?

That's not quite right. While something closely related to a subject is important to understanding it, we don't call it the subject itself.

Here are some terms for things closely related to a subject:

* Topic: This is a broad area of discussion or study, often encompassing several related subjects.

* Theme: This is a central idea or concept that runs throughout a piece of writing, a work of art, or a conversation.

* Aspect: This is a particular part or feature of a subject.

* Element: This is a component or part of something larger, like a subject.

* Subtopic: This is a smaller, more specific topic that falls within a larger subject.

Let me know if you'd like more information about any of these terms!