From The Collaborative International Dictionary of English v.0.48:
Elementary \El`e*men"ta*ry\, a. [L. elementarius: cf. F.
['e]l['e]mentaire.]
1. Having only one principle or constituent part; consisting
of a single element; simple; uncompounded; as, an
elementary substance.
[1913 Webster]
2. Pertaining to, or treating of, the elements, rudiments, or
first principles of anything; initial; rudimental;
introductory; as, an elementary treatise.
[1913 Webster]
3. Pertaining to one of the four elements, air, water, earth,
fire. "Some luminous and fiery impressions in the
elementary region." --J. Spencer.
[1913 Webster]