Easy, now especially in a disparaging sense; contemptibly easy.
Lazy, simplistic (especially of explanations, discussions etc.).
Effortless, fluent (of work, abilities etc.).
Of a reaction or other process, taking place readily.
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.