social worker vs welfare worker

social worker and welfare worker both are nouns.

Word	Noun	Adjective	Verb	Adverb
social worker	Yes	No	No	No
welfare worker	Yes	No	No	No

As nouns, social worker and welfare worker are synonyms defined as:

social worker and welfare worker: someone employed to provide social services (especially to the disadvantaged)

Other synonyms of social worker include caseworker.

social worker (noun)	welfare worker (noun)
someone employed to provide social services (especially to the disadvantaged)	someone employed to provide social services (especially to the disadvantaged)