ExpertS

It is not at all easy to say what an ''expert'' is.  This is actually studied in EpistemOlogy under the general heading ''ExpertKnowledge''.  On one account, put very roughly, an expert is a person who is (or, perhaps, is widely recognized to be) a reliable (see ReliabilIsm) source of KnowledgeByTestimony for other people.

Can be contrasted with CrankS, who think they know what they are talking about, but don't.  And with AcademicElitism, a syndrome of those who think that ONLY they know what they are talking about, and no one else does.