Profession is often restricted to include only those occupations requiring extensive study and possessing a specialized knowledge or theory base, such as law, medicine, nursing, the clergy or engineering.
Terms such as ocupational serve the purpose of uphelding the distinction between professionals and others who for their living are dependent on their work rather than on their economic wealth. Such usage avoids the confusion caused by vague usage of the words professional and professionalism to express prestige, approval or a sense of exclusivity.
Sociologists have been known to define professionalism as organised exclusivity along guild lines, much in the sense that George Bernard Shaw characterised all professions as "conspiracies against the laity".
A profession is always held by a person, and it is generally that person's way of generating income. Some historians believe that the foundation of modern civilization is division of labour into different professions, thus increasing the level of expertise held by professionals.
The existence of a traceable historical record of notable members of the profession is used as an indicator of a profession. Often, these historic professionals are well-known to laypersons outside the field, for example, Clarence Darrow (law), Edward Jenner (medicine), and Florence Nightingale (nursing.)
The distinction between laypersons and professionals denotes the critical aspect of more liberal definitions of a profession: being paid for the work. As such, ball players and movie makers may be professionals, although their work does not fit the strict definition offered above.
See also: list of professions