registrant vs worker

registrant and worker both are nouns.

Word	Noun	Adjective	Verb	Adverb
registrant	Yes	No	No	No
worker	Yes	No	No	No

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

registrant: a person who is formally entered (along with others) in a register (and who obtains certain rights thereby)
worker: a person who acts and gets things done

Other hypernyms of registrant include actor, doer.

registrant (noun)	worker (noun)
a person who is formally entered (along with others) in a register (and who obtains certain rights thereby)	sterile member of a colony of social insects that forages for food and cares for the larvae
	a person who works at a specific occupation
	a member of the working class (not necessarily employed)
	a person who acts and gets things done