person with more and deeper knowledge in a specific area, who is part of the leadership; for consultant use Q15978655 who is instead fulfilling functional roles

An advisor (or adviser) is someone who gives advice. (Someone who advises.) The job of an advisor is to give good advice that helps the person that he or she is advising. Usually, only certain people, like businessmen or politicians, have advisors. This is because these kinds of people are usually very busy, and they do not have the time to make decisions alone.

In the United States, the President's advisors are called his "Cabinet." Some well-known cabinet members, current and former, from the Bush Administration are: