viva voce vs oral exam

viva voce and oral exam both are nouns.

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

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

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

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

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

viva voce (adverb)	oral exam (adverb)
orally