social worker vs public servant

social worker and public servant both are nouns.

Word	Noun	Adjective	Verb	Adverb
social worker	Yes	No	No	No
public servant	Yes	No	No	No

As nouns, public servant is a hypernym of social worker; that is, public servant is a word with a broader meaning than social worker:

social worker: someone employed to provide social services (especially to the disadvantaged)
public servant: someone who holds a government position (either by election or appointment)

social worker (noun)	public servant (noun)
someone employed to provide social services (especially to the disadvantaged)	someone who holds a government position (either by election or appointment)