Foremost , to me , an expert is someone who has vast knowledge in his/her area of endeavor and is up-to-date , irrespective of whether the knowledge is acquired via formal or informal education.

What's your definition of an expert/professional in any field of endeavor ? You be in the know about the capabilities of the following two sets of people , which would you engage his/her service and why ? Sentiment apart !

1 ) Let me use for example ,western part of the country , where Yoruba is the dominant local dialect : Someone from the western part of the country in the filed of building technology , who acquired his knowledge in this industry through informal education and is handicapped in the use of refined English , thus can not sell his service to you through English expression .

2) Formally educated person in the same building industry , with well refined English abilities in his arsenal , but obviously lacking in the in-depth technical know-how - here, I'm referring to people who uses formal paper certificate and refined English language to gloss their ignorant .