oral vs viva

oral and viva both are nouns.

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

As nouns, oral and viva are synonyms defined as:

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

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

oral (adjective)	viva (adjective)
of or involving the mouth or mouth region or the surface on which the mouth is located
a stage in psychosexual development when the child's interest is concentrated in the mouth; fixation at this stage is said to result in dependence, selfishness, and aggression
of or relating to or affecting or for use in the mouth
using speech rather than writing