causal agent vs physical entity

causal agent and physical entity both are nouns.

Word	Noun	Adjective	Verb	Adverb
causal agent	Yes	No	No	No
physical entity	Yes	No	No	No

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

causal agent: any entity that produces an effect or is responsible for events or results
physical entity: an entity that has physical existence

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