1) any first thing, from which the others belonging to some series or composite whole take their rise, an element, first principal
1a) the letters of the alphabet as the elements of speech, not however the written characters, but the spoken sounds
1b) the elements from which all things have come, the material causes of the universe
1c) 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
1d) the elements, rudiments, primary and fundamental principles of any art, science, or discipline
1d1) i.e. of mathematics, Euclid's geometry
Part of Speech: noun neuter
Citing in TDNT: 7:670, 1087
Neuter of a presumed derivative of the base of G4748; something orderly in arrangement, that is, (by implication) a serial (basal, fundamental, initial) constituent (literally), proposition (figuratively): - element, principle, rudiment.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root στοιχεῖον; click on the second column to search for that grammatical form of the root στοιχεῖον; click on the third column to search for that word and grammatical form; click on the total to search for the root στοιχεῖον.