social organisation vs social system

social organisation and social system both are nouns.

Word	Noun	Adjective	Verb	Adverb
social organisation	Yes	No	No	No
social system	Yes	No	No	No

As nouns, social organisation and social system are synonyms defined as:

social organisation and social system: the people in a society considered as a system organized by a characteristic pattern of relationships

Other synonyms of social organisation include social organization, social structure, structure.

social organisation (noun)	social system (noun)
the people in a society considered as a system organized by a characteristic pattern of relationships	the people in a society considered as a system organized by a characteristic pattern of relationships