Primitive postpositions
Primitive (or simple) postpositions are monomorphemic and mostly monosyllabic.
The large majority of postpositions are primitive and monosyllabic and lack an etymology.
Complex postpositions
A complex postposition is one consisting of more than one morpheme. It may be a combination of primitive postpositions or a denominal postposition.
All complex postpositions are concrete postpositions; their postpositional phrases are adjuncts rather than complements.