What is a professional musician?

Is it someone with skill and/or talent? Maybe but some career musicians lack the previous characteristics and are still considered professional. Is it someone who gets paid to do music, i.e., the more money you make the more professional you are? This would make pop stars really professional and some argue that, at times, these characteristics are lacking. Is it the amount of time you dedicate to the art, although how do you then differentiate between the enthusiastic amateur and the professional? Is it the mind set that an artist has that makes them professional, e.g., one must be prepared, punctual, cordial and musically complementary. This seems like a must for professional musicians, yet some lack these basic skills and make up for it in talent/skill, while other amateurs are fully committed to the music and the lifestyle. I might argue that it is a combination of the facets above and that any professional musician combines the above traits to varying degrees. I do think that all those characteristics have to be there for one to call him or herself a professional musician.