only vs principal

only

adj
  • Singularly superior; the best. 

  • Alone in a category. 

  • Without sibling; without a sibling of the same gender. 

adv
  • As recently as. 

  • Without others or anything further; exclusively. 

  • Used to express surprise or consternation at an action. 

  • Introduces a disappointing or surprising outcome that renders futile something previously mentioned. 

  • No more than; just. 

noun
  • An only child. 

conj
  • Under the condition that; but. 

  • But; except. 

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 only and principal occurred in a corpus of books? (source: Google Ngram Viewer )