principal

/ˈprin(t)-s(ə-)pəl/

Middle English, from Anglo-French, from Latin principalis, from princip-, princeps

adjective

  1. most important, consequential, or influential : chief

  2. of, relating to, or constituting principal or a principal

the principal ingredient

noun

  1. a person who has controlling authority or is in a leading position: such as

  2. a chief or head man or woman

  3. the chief executive officer of an educational institution

noun

  1. the diagonal in a square matrix that runs from upper left to lower right