primary vs principal

primary

noun
  • Any flight feather attached to the manus (hand) of a bird. 

  • A directly driven inductive coil, as in a transformer or induction motor that is magnetically coupled to a secondary 

  • A primary school. 

  • A primary election; a preliminary election to select a political candidate of a political party. 

  • A radar return from an aircraft (or other object) produced solely by the reflection of the radar beam from the aircraft's skin, without additional information from the aircraft's transponder. 

  • A base or fundamental component; something that is irreducible. 

  • The most massive component of a gravitationally bound system, such as a planet in relation to its satellites. 

  • The first year of grade school. 

  • A primary colour. 

  • Primary site of disease; original location or source of the disease. 

  • The first stage of a thermonuclear weapon, which sets off a fission explosion to help trigger a fusion reaction in the weapon's secondary stage. 

adj
  • Earliest formed; fundamental. 

  • first or earliest in a group or series. 

  • main; principal; chief; placed ahead of others. 

  • Relating to day-to-day care provided by health professionals such as nurses, general practitioners, dentists etc. 

  • Relating to the place where a disorder or disease started to occur. 

  • Illustrating, possessing, or characterized by, some quality or property in the first degree; having undergone the first stage of substitution or replacement. 

verb
  • To challenge (an incumbent sitting politician) for their political party's nomination to run for re-election, through running a challenger campaign in a primary election, especially one that is more ideologically extreme. 

  • To take part in a primary election. 

principal

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

  • 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. 

  • 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 

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

  • Primary; most important; first level in importance. 

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