following an occupation as a means of livelihood or for gain

a professional builder.

of, pertaining to, or connected with a profession

professional studies.

appropriate to a profession

professional objectivity.

engaged in one of the learned professions

A lawyer is a professional person.

following as a business an occupation ordinarily engaged in as a pastime

a professional golfer.

making a business or constant practice of something not properly to be regarded as a business

A salesman, he said, is a professional optimist.

undertaken or engaged in as a means of livelihood or for gain

professional baseball.

of or for a professional person or his or her place of business or work

a professional apartment; professional equipment.

done by a professional; expert

professional car repairs.

a person who belongs to one of the professions, esp. one of the learned professions.

a person who earns a living in a sport or other occupation frequently engaged in by amateurs

a golf professional.

an expert player, as of golf or tennis, serving as a teacher, consultant, performer, or contestant; pro.

a person who is expert at his or her work

You can tell by her comments that this editor is a real professional.