incident vs principal

incident

adj
  • Dependent upon, or appertaining to, another thing, called the principal. 

  • Liable to happen; apt to occur; befalling; hence, naturally happening or appertaining. 

  • Arising as the result of an event, inherent. 

  • Coming or happening accidentally; not in the usual course of things; not in connection with the main design; not according to expectation; casual; fortuitous. 

  • Falling on or striking a surface. 

noun
  • An event that causes or may cause an interruption or a crisis, such as a workplace illness or a software error. 

  • A (relatively minor) event that is incidental to, or related to others. 

  • An event or occurrence. 

principal

adj
  • Primary; most important; first level in importance. 

  • Chosen or assumed among a branch of possible values of a multi-valued function so that the function is single-valued. 

noun
  • The chief administrator of a school. 

  • A diapason, a type of organ stop on a pipe organ. 

  • The construction that gives shape and strength to a roof, generally a truss of timber or iron; or, loosely, the most important member of a piece of framing. 

  • A dancer at the highest rank within a professional dance company, particularly a ballet company. 

  • The primary participant in a crime. 

  • The first two long feathers of a hawk's wing. 

  • A security principal. 

  • A legal person that authorizes another (the agent) to act on their behalf; or on whose behalf an agent or gestor in a negotiorum gestio acts. 

  • The chief executive and chief academic officer of a university or college. 

  • The money originally invested or loaned, on which basis interest and returns are calculated. 

  • A partner or owner of a business. 

  • One of the turrets or pinnacles of waxwork and tapers with which the posts and centre of a funeral hearse were formerly crowned 

How often have the words incident and principal occurred in a corpus of books? (source: Google Ngram Viewer )