Thayer's Greek Lexicon

 1. any first thing, from which the others belonging to some series or
composite whole take their rise, an element, first principal
  1) the letters of the alphabet as the elements of speech, not
however the written characters, but the spoken sounds
  2) the elements from which all things have come, the material
causes of the universe
  3) the heavenly bodies, either as parts of the heavens or (as
others think) because in them the elements of man, life and
destiny were supposed to reside
  4) the elements, rudiments, primary and fundamental principles
of any art, science, or discipline
1d1. i.e. of mathematics, Euclid's geometry