1
general::
spoken
used about the language that people speak rather than write:
• Spoken English is often less formal than written English. • I can understand classical Arabic but not spoken Arabic.
oral
an oral test is one in which you have to speak rather than write. Oral is also used about culture, traditions, and history that are based on spoken English rather than being written down:
• We had a 15-minute oral exam in German. • Anglo-Saxon stories and poems were part of a largely oral culture.
verbal
a verbal agreement, warning, form of communication etc is spoken rather than written down:
• We had a verbal agreement but no written contract. • The company have received verbal approval to begin the project.
by/through word of mouth
by someone telling you about something rather than by reading about it somewhere - used to say how you got some information:
• He found out about the job by word of mouth. • A lot of our customers hear about us through word of mouth.
Longman-Thesaurus