primum mobile vs first cause

primum mobile and first cause both are nouns.

Word	Noun	Adjective	Verb	Adverb
primum mobile	Yes	No	No	No
first cause	Yes	No	No	No

As nouns, primum mobile and first cause are synonyms defined as:

primum mobile and first cause: an agent that is the cause of all things but does not itself have a cause

Other synonyms of primum mobile include prime mover.

primum mobile (noun)	first cause (noun)
an agent that is the cause of all things but does not itself have a cause	an agent that is the cause of all things but does not itself have a cause