systems theory vs subject

systems theory and subject both are nouns.

Word	Noun	Adjective	Verb	Adverb
systems theory	Yes	No	No	No
subject	Yes	Yes	Yes	No

As nouns, subject is a hypernym of systems theory; that is, subject is a word with a broader meaning than systems theory:

systems theory: the interdisciplinary study of systems in general, with the goal of elucidating principles that can be applied to all types of systems at all nesting levels in all fields of research.
subject: a branch of knowledge

Other hypernyms of systems theory include bailiwick, discipline, field, field of study, study, subject area, subject field.

systems theory (noun)	subject (noun)
the interdisciplinary study of systems in general, with the goal of elucidating principles that can be applied to all types of systems at all nesting levels in all fields of research.	something (a person or object or scene) selected by an artist or photographer for graphic representation
	a branch of knowledge
	some situation or event that is thought about
	the subject matter of a conversation or discussion
	(grammar) one of the two main constituents of a sentence; the grammatical constituent about which something is predicated
	(logic) the first term of a proposition
	a person who owes allegiance to that nation
	a person who is subjected to experimental or other observational procedures; someone who is an object of investigation

systems theory (adjective)	subject (adjective)
	likely to be affected by something
	being under the power or sovereignty of another or others
	possibly accepting or permitting

systems theory (verb)	subject (verb)
	make accountable for
	cause to experience or suffer or make liable or vulnerable to
	make subservient; force to submit or subdue