Basic, fundamental or elementary.
Of, or relating to a force of nature, especially to severe atmospheric conditions.
Of, relating to, or being an element (as opposed to a compound).
Of the ancient supposed elements of earth, air, fire and water.
A creature (usually a spirit) that is attuned with, or composed of, one of the classical elements: air, earth, fire and water or variations of them like ice, lightning, etc. They sometimes have unique proper names and sometimes are referred to as Air, Earth, Fire, or Water.
Single, simple; not complex.
Unidirectional.
A monomorphemic word, one without affixes.
An analogue in a space of arbitrary dimensionality of the triangle or tetrahedron; the convex hull of n+1 linearly independent points in n-dimensional space; in other words, the triangle, tetrahedron etc., generalized to an arbitrary number of dimensions.