A registered professional engineer can get certified as such and never make a penny doing it. He's still very much a pro. There are many certifications that this applies to. Maybe a buddy gives me a dollar for a homebrew. Am I a pro? Not in my book.
"pro·fes·sion·al [pruh-fesh-uh-nl] Show IPA
1. following an occupation as a means of livelihood or for gain: a professional builder.
2. of, pertaining to, or connected with a profession: professional studies.
3. appropriate to a profession: professional objectivity.
4. engaged in one of the learned professions: A lawyer is a professional person.
5. following as a business an occupation ordinarily engaged in as a pastime: a professional golfer."
"am·a·teur [am-uh-choor, -cher, -ter, am-uh-tur] Show IPA
1. a person who engages in a study, sport, or other activity for pleasure rather than for financial benefit or professional reasons. Compare professional.
2. an athlete who has never competed for payment or for a monetary prize."