Profession

n.
  1. The act of professing or claiming; open declaration; public avowal or acknowledgment; as, professions of friendship; a profession of faith.
  2. That which one professed; a declaration; an avowal; a claim; as, his professions are insincere.
  3. That of which one professed knowledge; the occupation, if not mechanical, agricultural, or the like, to which one devotes one's self; the business which one professes to understand, and to follow for subsistence; calling; vocation; employment; as, the profession of arms; the profession of a clergyman, lawyer, or physician; the profession of lecturer on chemistry.
  4. The collective body of persons engaged in a calling; as, the profession distrust him.
  5. (Eccl. Law.) The act of entering, or becoming a member of, a religious order.

The three professions, or learned professions, are, especially, theology, law, and medicine.