simian vs primate

simian and primate both are nouns.

Word	Noun	Adjective	Verb	Adverb
simian	Yes	Yes	No	No
primate	Yes	No	No	No

As nouns, primate is a hypernym of simian; that is, primate is a word with a broader meaning than simian:

simian: an ape or monkey
primate: any placental mammal of the order Primates; has good eyesight and flexible hands and feet

simian (noun)	primate (noun)
an ape or monkey	any placental mammal of the order Primates; has good eyesight and flexible hands and feet
	a senior clergyman and dignitary

simian (adjective)	primate (adjective)
relating to or resembling an ape