oral fissure vs rima oris

oral fissure and rima oris both are nouns.

Word	Noun	Adjective	Verb	Adverb
oral fissure	Yes	No	No	No
rima oris	Yes	No	No	No

As nouns, oral fissure and rima oris are synonyms defined as:

oral fissure and rima oris: the opening through which food is taken in and vocalizations emerge

Other synonyms of oral fissure include mouth, oral cavity.

oral fissure (noun)	rima oris (noun)
the opening through which food is taken in and vocalizations emerge	the opening through which food is taken in and vocalizations emerge