oral exam vs viva voce

oral exam and viva voce both are nouns.

Word	Noun	Adjective	Verb	Adverb
oral exam	Yes	No	No	No
viva voce	Yes	No	No	Yes

As nouns, oral exam and viva voce are synonyms defined as:

oral exam and viva voce: an examination conducted by spoken communication

Other synonyms of oral exam include oral, oral examination, viva.

oral exam (noun)	viva voce (noun)
an examination conducted by spoken communication	an examination conducted by spoken communication

oral exam (adverb)	viva voce (adverb)
	orally