causal agent vs worker

causal agent and worker both are nouns.

Word	Noun	Adjective	Verb	Adverb
causal agent	Yes	No	No	No
worker	Yes	No	No	No

As nouns, worker is a hyponym of causal agent; that is, worker is a word with a more specific, narrower meaning than causal agent:

causal agent: any entity that produces an effect or is responsible for events or results
worker: a person who acts and gets things done

causal agent (noun)	worker (noun)
any entity that produces an effect or is responsible for events or results	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