Elementary

1. a. Pertaining to one of the four elements, air, water, earth, fire.
2. a. Having only one principle or constituent part; consisting of a single element; simple; uncompounded; as, an elementary substance.
3. a. Pertaining to, or treating of, the elements, rudiments, or first principles of anything; initial; rudimental; introductory; as, an elementary treatise.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.