Education

• Principal (school), a head of a primary or secondary school
• Principal (academia)
  Principal (academia)
  The Principal is the chief executive and the chief academic officer of a university or college in certain parts of the Commonwealth.-Canada:...
  
  , a chief executive of a university or college

Law

• Principal (commercial law), a person who authorises an agent
• Principal (criminal law)
  Principal (criminal law)
  Under criminal law, a principal is any actor who is primarily responsible for a criminal offense. Such an actor is distinguished from others who may also be subject to criminal liability as accomplices, accessories or conspirators....
  
  , a primary actor in a criminal offense

Science

• Principal Investigator
  Principal investigator
  A principal investigator is the lead scientist or engineer for a particular well-defined science project, such as a laboratory study or clinical trial....
  
  , a lead scientist or engineer for a field
• Principal value
  Principal value
  In considering complex multiple-valued functions in complex analysis, the principal values of a function are the values along one chosen branch of that function, so it is single-valued.-Motivation:...
  
  , a value along a chosen branch of a multivalued function
• Principal branch
  Principal branch
  In mathematics, a principal branch is a function which selects one branch, or "slice", of a multi-valued function. Most often, this applies to functions defined on the complex plane: see branch cut....
  
  , a special selected branch of a multivalued function
• Principal ideal
  Principal ideal
  In ring theory, a branch of abstract algebra, a principal ideal is an ideal I in a ring R that is generated by a single element a of R.More specifically:...
  
  , an ideal with a single generator, and the related concept of principal ideal domains
• Cauchy principal value
  Cauchy principal value
  In mathematics, the Cauchy principal value, named after Augustin Louis Cauchy, is a method for assigning values to certain improper integrals which would otherwise be undefined.-Formulation:...
  
  , a way of assigning a finite value to improper integrals that seem to diverge

Performing arts

• Principal dancer
  Principal dancer
  A principal dancer is a dancer at the highest rank within a professional dance company, particularly a ballet company....
  
  , a high-ranked dancer in a ballet company
• The Principal, or Diapason, an organ stop on a pipe organ
• Principal, the lead of a section of an orchestra

Places

• Principal, Cape Verde, a village
• Principal, Ecuador, a parish in Azuay Province
  Azuay Province
  Azuay is a province of Ecuador, created 25 June 1824. It encompasses an area of . Its capital is Cuenca. It is located in the south center of Ecuador in the highlands. Its mountains reach above sea level in the national park of El Cajas....
  
  , Ecuador

Other uses

• Principal (architecture)
• Principal (computer security), an entity that can be identified and verified
• Principal sum, the original amount of a debt or investment on which interest is calculated
• The Principal
  The Principal
  The Principal is a 1987 action film, starring James Belushi and Louis Gossett, Jr. It was written by Frank Deese and directed by Christopher Cain, and filmed in Oakland, California.-Plot:...
  
  , a 1987 action film
• Principal Financial Group
  Principal Financial Group
  Principal Financial Group is a publicly traded corporation based in Des Moines, Iowa, USA.The Principal Financial Group is a global financial services provider which offers a wide range of financial products and services, and is a U.S. leader in 401 plans. Headquartered in Des Moines, Iowa, the...
  
  , a life insurance company traded on the NYSE
• Dean (Christianity) or principal, the head of a cathedral or collegiate church
• Principal (civil service) or principal officer, a senior management grade in Her Majesty's Civil Service