What does SUBJECT mean?

noun

1. the subject matter of a conversation or discussion“he didn't want to discuss that subject”
2. something (a person or object or scene) selected by an artist or photographer for graphic representation“a moving picture of a train is more dramatic than a still picture of the same subject”
3. a branch of knowledge“in what discipline is his doctorate?”
4. some situation or event that is thought about“he kept drifting off the topic”
5. (grammar) one of the two main constituents of a sentence; the grammatical constituent about which something is predicated
6. a person who is subjected to experimental or other observational procedures; someone who is an object of investigation“the subjects for this investigation were selected randomly”
7. a person who owes allegiance to that nation“a monarch has a duty to his subjects”
8. (logic) the first term of a proposition