The core syntactic property of adjectives is that they can be used attributively and/or predicatively. However, many adjectives can also be used adverbially, i.e. as modifiers of verbal, adjectival or prepositional projections. An attributively used adjective can be easily distinguished from an adverbially used adjective because only the former has the attributive -e ending, but there is no morphological distinction in Dutch between predicatively and adverbially used adjectives. Therefore, it is often only on the basis of the meaning contribution of the adjective (i.e. by determining whether it modifies a noun phrase or some other category) that we can distinguish its adverbial use. For example, the attributive adjectives geweldiggreat, snelquick and diepdeep from the primeless examples in (2) are used adverbially in the primed examples: the modification involves a VP in (2a'), an AP in (2b') and a PP in (2c'). This section discusses such cases in more detail.

Although Dutch does not have a formal marker for adverbially used adjectives comparable to the English adverbial -ly suffix, adverbially used adjectives can sometimes be recognized by their morphological composition: adjectives ending in the affixes in (3) are used only in adverbial function, with the exception of some incidental cases of the type in (3a), which can also be used predicatively: cf. Hij is wat gewoontjesHe is a bit common. We refer the reader to De Haas and Trommelen (1993:352ff.) and Booij (2015b) for further discussion of the forms in (3).

The examples in (4) provide some more or less fixed phrasal expressions that are mainly used adverbially; cf. also the discussion of (26) and (27) in Section 30.2.2, sub II below.

Before we begin the more detailed discussion of the adverbial use of the adjective, a warning flag must be hoisted. This chapter discusses many adverbs for which there is no clear or direct evidence that they are actually adjectives. Consider the time/frequency adverbs in (5).

The syntactic distribution of these adverbs gives no indication of their categorial status: they can only be used adverbially, as in (6a), but this function can also be performed by a noun phrase, as in (6b).

Therefore, we have to rely on other means for determining the category of these adverbs, e.g. by examining whether modification by a degree modifier such as zeervery or comparative/superlative formation is possible. Only for the adverb vaak does this provide conclusive evidence that it is an adjective: as shown in (7), it can be preceded by a degree modifier like zeervery or heelvery, and it can undergo comparative/superlative formation.

For the adverb somssometimes, there is only weak evidence that it is an adjective: it can be amplified by heel, but amplification by zeer and comparative/superlative formation are excluded.

For altijdalways and nooitnever, there is no such evidence at all: the examples in (9) show that both degree modification and superlative/comparative formation are excluded.

Although we have no conclusive evidence for the adjectival status of soms, altijd and nooit, it seems reasonable to assume that they have the same categorial status as vaak, for at least two reasons. First, there is no evidence that these adverbs have a different categorial status. Second, one might assume that degree modification and comparative/superlative formation of altijdalways and nooitnever are blocked because they are quantificational in nature. Altijd functions as a universal temporal quantifier (∀t) and nooit functions as a negative existential quantifier (¬∃t), and the absolute nature of the quantificational force of these adverbs may thus be responsible for blocking degree modification and comparative/superlative formation. Note that such evidence is circumstantial and should be treated with caution.

Although we will tentatively treat adverbs as adjectives, it should be noted that there is a striking difference between adverbs and adjectives in predicative functions; the former do not take complements. For example, the complementive gehoorzaamobedient in (10a) can take a PP-complement such as aan de wetto the law, but this is not possible in (10b), in which gehoorzaam functions as a manner adverb.

In (11), the contrast is somewhat obscured by the fact that the two (b)-examples are both acceptable: example (11b) is ambiguous between an adverbial and a supplementive reading of the adjective; the number sign # in (11b') is used to express that the PP-complement is only possible in the supplementive (i.e. predicative) reading, a judgment based mainly on intuition.