Oral, verbal are often confused in use.
Oral (see also VOCAL 1 ) implies utterance and speech; it is distinctively applicable to whatever is delivered, communicated, transacted, or carried on directly from one to another by word of mouth.
Verbal stresses the use of words and may apply indifferently to what is written or spoken, for it carries no implication of the method of communication.
The use of verbal as a substitute for oral fails to convey the intended distinction or suggests unintended or irrelevant distinctions or contrasts; thus, one would speak of an oral invitation or oral testimony when spoken is to be implied, because verbal would be ambiguous.