Adverbial phrases differ from arguments in that they are optional in the prototypical case. There are cases, however, in which a verb is obligatorily accompanied by an adverbial-like phrase. A typical instance is the verb wonen'to live' in (223), which must be combined with a locational PP or an AP denoting a property of the accommodation or the surroundings where the subject of the clause lives.

It is not immediately clear that the syntactic function of the PPs and APs is really adverbial. They are often called complements because the verb normally cannot occur without them, which takes the selectional property of the verb to be of a syntactic nature. However, this conclusion is perhaps too easy, given that the obligatory presence of a PP/AP may also be due to pragmatics: in accordance with Grice’s cooperative principle, the sentence Jan woont may be dismissed as uninformative because the proposition expressed by it is already presupposed to be true for all people. The same is true for examples with geboren worden: an example such as Jan is geboren is simply not informative; another similar case is zich gedragen ‘to behave’, which only occurs without an adverbial phrase in imperatives if the behavior of the addressee is inappropriate: Gedraag je! ‘Behave yourself!’.

The same may hold for verbs selecting measure phrases like duren'to last', kosten'to cost', meten'to measure' and wegen'weigh', which were discussed in Section 2.4. Example (225a) shows for duren that these verbs normally need an extra constituent that evidently does not function as argument; omitting the addition results in an uninformative sentence as performances always have some duration. That this account may be on the right track is suggested by examples such as (225a): the sentence Het vriest'It freezes' is informative in itself and consequently does allow omission of the measure phrase.

We conclude from the discussion above that adverbial phrases are always optional as far as syntax is concerned, but that there may be pragmatic reasons for obligatorily including an adverbial phrase with certain verbs.