monism vs philosophical system

monism and philosophical system both are nouns.

Word	Noun	Adjective	Verb	Adverb
monism	Yes	No	No	No
philosophical system	Yes	No	No	No

As nouns, philosophical system is a hypernym of monism; that is, philosophical system is a word with a broader meaning than monism:

monism: the doctrine that reality consists of a single basic substance or element
philosophical system: a belief (or system of beliefs) accepted as authoritative by some group or school

Other hypernyms of monism include doctrine, ism, philosophy, school of thought.

monism (noun)	philosophical system (noun)
the doctrine that reality consists of a single basic substance or element	a belief (or system of beliefs) accepted as authoritative by some group or school