The core property of adjectives is that they can be used attributively and/or predicatively. However, many adjectives can also be used adverbially, that is, 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. There is, however, no morphological distinction in Dutch between predicatively and adverbially used adjectives. Therefore, it is only on the basis of the meaning contribution of the adjective (that is, by determining whether it modifies a noun phrase or some other category) that we can distinguish the adverbial use of the adjective. For example, the attributively used adjectives geweldig'great', snel'quick' and diep'deep' 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 cases like these in more detail.

      Although Dutch does not have a formal marker of adverbially used adjectives like the English adverbial -ly suffix, adverbially used adjectives can sometimes be recognized on the basis of their morphological makeup: adjectives that end in the affixes in (3) are only used in adverbial function with the exception of some incidental formations of type in (3a), which can also be used predicatively: Hij is wat gewoontjes'He is a bit common'. We refer the reader to De Haas and Trommelen (1993:352ff.) for a more extensive discussion of the forms in (3).

The examples in (4) provide some, more or less fixed, phrasal expressions that are mainly used adverbially; see also the discussion of (25) and (26) in Section 8.2.1, sub II below.

      Before we start the more detailed discussion of the adverbial use of the adjective, a warning flag must be raised. In this chapter, many adverbs are discussed for which there is no conclusive or direct evidence that they are actually adjectives. Take as an example the adverbs of time/frequency in (5).

The syntactic distribution of these adverbs does not provide any clue about their categorial status: they can only be used adverbially, but as is shown in (6a), this function can also be performed by a noun phrase.

Therefore, we have to appeal to other means in order to determine the category of these adverbs, for instance, by investigating whether modification by an intensifier like zeer'very' or comparative/superlative formation is possible. Only for the adverb vaak does this provides conclusive evidence that it is an adjective: as is shown in (7), it can be preceded by an intensifier like zeer'very' or heel'very', and it can undergo comparative/superlative formation.

For the adverb soms'sometimes', there is only weak evidence that it is an adjective: it can be intensified by heel, but intensification by zeer and comparative/superlative formation are excluded.

For altijd'always' and nooit'never', evidence of this sort is completely lacking: the examples in (9) show that intensification and superlative/comparative formation are both excluded.

Despite the fact that conclusive evidence for assuming adjectival status for soms, altijd and nooit is missing, it seems reasonable to assume that they have the same categorial status as vaak. There are two reasons for this. First, evidence that these adverbs have another categorial status is missing as well. Second, one could assume that intensification and comparative/superlative formation of altijd'always' and nooit'never' are blocked due to the fact that they are quantificational in nature. Altijd functions as a universal quantifier over time (∀t) and nooit functions as a negative existential quantifier over time (¬∃t), and the absolute nature of the quantificational force of these adverbs may be responsible for blocking intensification and comparative/superlative formation. Evidence of this sort is only circumstantial, however, and should therefore be handled with care.
      Although we will categorically treat adverbs as adjectives, it should be noted that there is a conspicuous difference between adverbially used adjectives and adjectives in other functions. The former never take complements. This is illustrated in (10); the predicatively used adjective nieuwsgierig'curious' in (10a) can take a prepositional complement like naar de uitslag'about the results', but this is not possible in (10a') where it is used as a manner adverb. A similar contrast can be found in the (b)-examples.