prime mover vs causal agent

prime mover and causal agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
prime mover	Yes	No	No	No
causal agent	Yes	No	No	No

As nouns, causal agent is a hypernym of prime mover; that is, causal agent is a word with a broader meaning than prime mover:

prime mover: an agent that is the cause of all things but does not itself have a cause
causal agent: any entity that produces an effect or is responsible for events or results

Other hypernyms of prime mover include causal agency, cause.

prime mover (noun)	causal agent (noun)
an agent that is the cause of all things but does not itself have a cause	any entity that produces an effect or is responsible for events or results