1. reality principle the governing principle of the ego
  2. principle a basic generalization that is accepted as true
  3. principal main or most important
  4. life principle a hypothetical force to which the functions and qualities peculiar to living things are sometimes ascribed
  5. first principle the elementary stages of any subject (usually plural)
  6. moral principle the principle that conduct should be moral
  7. vital principle a hypothetical force to which the functions and qualities peculiar to living things are sometimes ascribed
  8. pleasure principle the governing principle of the id
  9. legal principle a principle underlying the formulation of jurisprudence
  10. basic principle principles from which other truths can be derived
  11. in principle with regard to fundamentals although not concerning details
  12. working principle a rule that is adequate to permit work to be done
  13. uncertainty principle (quantum theory) the theory that it is impossible to measure both energy and time (or position and momentum) completely accurately at the same time
  14. petitio principii the logical fallacy of assuming the conclusion in the premises; begging the question
  15. bitter principle any one of several hundred compounds having a bitter taste
  16. Le Chatelier principle the principle that if any change is imposed on a system that is in equilibrium then the system tends to adjust to a new equilibrium counteracting the change
  17. past participle a participle that expresses completed action
  18. present participle a participle expressing present action
  19. Archimedes' principle (hydrostatics) the apparent loss in weight of a body immersed in a fluid is equal to the weight of the displaced fluid
  20. exclusion principle no two electrons or protons or neutrons in a given system can be in states characterized by the same set of quantum numbers