A circumposition is a discontinuous adposition. E1 shows an example from German:

um ... willen is a circumposition. The permutation is shown in order to demonstrate constituent status for the circumpositional phrase.

A circumpositional phrase has the structure of the adpositional phrase (AdpP) in S1:

A circumposition is an adposition of the form of A ... B in a construction of the form of S1. For A ...B to qualify as a circumposition, the construction must not be analyzable as either S2.a or b.

Y in S2 is any phrasal category, e.g. AdpP or NP. A circumposition does not (synchronically) consist of a preposition and a postposition; a circumpositional phrase does not consist of a postpositional phrase governed by a preposition or vice versa.

To return to E1, both of the parts of um ... willen are necessary in the construction; both um NP_Gen and NP_Gen willen are ungramatical outside this particular construction.

Diagnostic criteria for circumposition status of A...B include the following:

1. Neither A nor B can be substituted (by other adpositions) freely and regularly in the construction.
2. Neither A nor B may be omitted in a semantically regular way in the construction.
3. The relational meaning is non-compositional. That is, even if either A or B occur independently (as adpositions or adverbs), then the meaning that they have in isolation plays no role in the combination A...B.
4. A...B is in a substitution class with simple adpositions. Thus, S1 may be substituted by either of the following:
   • [ [C]Prep [X]NP ]PrepP
   • [ [X]NP [C]Postp ]PostpP
   such as wegen des lieben Friedens and des lieben Friedens halber, respectively, both ‘because of dear peace’.

Stacked binary combinations of the type S2 are a frequent diachronic source of circumpositional constructions. For instance, the German circumpositions um ... willen ‘for the sake of’, von ... wegen ‘on behalf of’ (von Amts/Rechts wegen ‘officially/legally’) and an ... statt ‘instead’ (an Kindes statt ‘as a child’) stem from earlier prepositional phrases, as follows:

• [ um [ [X]_NP.Gen willen ]_NP.Dat ]_PP ‘for X's will’;
• [ von [ [X]_NP.Gen wegen ]_NP.Dat ]_PP ‘from X's ways’;
• [ an [ [X]_NP.Gen statt ]_NP.Dat ]_PP ‘in X's stead’.

As long as the constructions can be analyzed in this way, there is not yet any circumposition. Thus, a circumposition arises by reanalysis of a syntactically more complex construction and accompanying lexicalization of the discontinuous combination of the two relators into one lexical item.