[WikiEN-l] What is your definition of an "expert"?

[Daniel P. B. Smith]

The dictionary says: A person with a high degree of skill in or  
knowledge of a certain subject.

Perhaps the question you meant to ask is, how do I tell whether or  
not a person is an expert?

Here's my personal answer.

1) I regard someone as an expert if they can show me that they can  
accurately convey detailed information on a topic directly from  
memory, and when needed can remember or quickly rediscover the source  
from which they that got that information. Think of a lawyer who  
cites a legal decision, or a minister who can literally "cite chapter  
and verse."

2) Someone who has done so much valuable work on a topic that he is  
cited as a source by many others, either formally (in a print  
citation) or informally (someone telling you "go see so-and-so about  
that.")