A calling requiring specialized knowledge and often long and intensive preparation including instruction in skills and methods as well as the scientific, historical, or scholarly principles underlying such skills and methods, maintaining by force of organization or concerted opinion high standards of achievement and conduct, and committing its members to continued study and to a kind of work which has for its prime purpose the rendering of public service…

Important components of being a professional …

  1. A calling
  2. Specialized knowledge
  3. Long and intensive preparation
  4. Instruction in skills and methods (performance and knowledge)
  5. Belonging to an organization
  6. Lifelong learning
  7. Purpose of rendering public service

from Webster's New World Dictionary (1966)