oral exam vs examination

oral exam and examination both are nouns.

Word	Noun	Adjective	Verb	Adverb
oral exam	Yes	No	No	No
examination	Yes	No	No	No

As nouns, examination is a hypernym of oral exam; that is, examination is a word with a broader meaning than oral exam:

Other hypernyms of oral exam include exam, test.

oral exam (noun)	examination (noun)
an examination conducted by spoken communication	the act of examining something closely (as for mistakes)
	the act of giving students or candidates a test (as by questions) to determine what they know or have learned
	a detailed inspection of your conscience (as done daily by Jesuits)
	a set of questions or exercises evaluating skill or knowledge
	formal systematic questioning