The adjectival modal adverbs are expressions of the degree of probability/plausibility that the proposition expressed by the clause is true. Some typical examples of such adverbs are given in (21).

In (22) two examples are given in context; the paraphrases in the primed examples show that we are indeed dealing with modification of the full clause.

The fact that the heads of the adverbial phrases in (22) can be modified by the degree modifier heel/zeervery unambiguously shows that they are adjectives. However, with the exception of (zeer) beslistdefinitely, it is not possible to use a degree modifier with the other adverbs in (21). Nevertheless, there are other indications that they are adjectival in nature: the elements blijkbaar, schijnbaar, natuurlijk and vermoedelijk, for example, contain the adjectivizing affixes -baar and -lijk.

Despite the fact that the adverbs in (22) can be modified by a degree modifier, comparative formation is excluded. This is particularly conspicuous in the case of the adjective waarschijnlijk, which normally allows the comparative form. This contrast has already been illustrated in example (14) in Section 30.2, sub I, which shows that on- prefixation of adverbially used waarschijnlijk is also excluded.

The adjectival subjective adverbs express a subjective evaluation by the speaker of the assertion expressed by the clause. Some typical examples are given in (23).

The primeless examples in (24) provide some sentences with these adverbs; their paraphrases are given in the primed examples.

The subjective adjectives in (23) cannot be modified by a degree modifier or undergo comparative formation in their subjective reading; they are also special in that they do not allow on- prefixation. This is illustrated in (25) by gelukkig, which normally allows these processes. Example (25a) is ambiguous: the adjective gelukkig is either interpreted as a clause adverbial, in which case it expresses relief on the part of the speaker, or it is used as a VP (manner) adverbial, in which case it indicates that the fall has no serious consequences. In the examples in (25b-d) it can only be interpreted as a manner adverbial.

For completeness’ sake, it should be noted that the subjective adverb gelukkig has a negative counterpart, which is realized as an adverbial form in –erwijs, as in De onsportieve atleet is ongelukkigerwijs ten val gekomen Unfortunately, the unfair athlete fell; cf. also the discussion of (3a) above and (27b) below.

Since subjective adverbs cannot be modified by a degree modifier, it is difficult to establish for some of the adverbs in (23) that they are really adjectives. However, the fact that onverhoopt (which has no positive counterpart) is prefixed with the negative marker on- strongly suggests that it is indeed an adjective; cf. Section 23.3.1, sub II. The same is suggested by the fact that hopelijk contains the adjectivizing affix -elijk. Another indication that we are dealing with adjectives is that some subjective clause adverbials can be modified by the degree element genoeg; indeed, the addition of this element in example (25a), as in (26a), strongly favors the interpretation of the adjective as a clause adverbial. Recall that the modifier genoegenough can license an infinitival om-clause when it modifies, for example, an attributive adjective. This is impossible, however, when it modifies a clause adverbial; adding an om-clause to (26a) forces an interpretation of the adjective as a VP adverbial.

A remarkable property of genoeg is that it allows certain adjectives to be used as clause adverbials, which otherwise cannot be used in this function; example (25d) has shown that the negative adjective ongelukkig cannot normally be interpreted as a clause adverbial, but if we add genoeg, as in (27a), this interpretation becomes readily available. Example (27b) shows that a similar effect occurs when we add the affix -erwijs to this adjective.

Diepeveen (2009) has shown that genoeg also has the ability to transform basic adjectives such as interessantinteresting, which cannot normally be used adverbially, into subjective adverbs. Some of her examples are given in (28).

The third type of adjecties typically used as clause adverbials are the frequency adverbs in (29), which differ from time adverbs such as laatlate in that they do not locate the eventuality in a specific interval on the time axis, but indicate the frequency of the state of affairs.

These frequency adverbs can function as clause adverbials, as can be seen from the fact, illustrated in (30), that they can occur in the het is adverb zo dat ... frame. However, we will return to frequency adverbs in Section 30.2.3, sub III, and show that they can also be used as VP adverbials.

Most of the frequency adverbs in (29) are adjectival in nature; many of them can be modified by a degree modifier or a quantifier, as shown in (31).

That dagelijks, wekelijks and maandelijks are adjectives is beyond doubt, given that they can also occur in attributive position; cf. (32). Finally, that gewoonlijk is adjectival is plausible, since it contains the adjectival affix -lijk.

In some cases, however, it is not possible to determine the categorial status of frequency adverbs because they do not allow modification or comparative formation.

The examples in (34) show that adverbial phrases of time such as laatlate cannot be used as clause adverbials; Section 30.2.3, sub II, will show that such adverbs function as VP adverbials.

Nevertheless, there are certain adverbial phrases of time that can sometimes function as clause adverbials, as shown in (35) with the adverbial PP op zondagon Sunday.

The (b)-examples in (34) and (35) show that the difference in function is reflected in the position of these adverbial phrases relative to the frequency adverb vaakoften: while the VP adverbial phrase laatlate follows the frequency adverb, the adverbial phrase op zondagon Sunday precedes it. The semantic contributions of the two adverbial phrases are also different: while laat locates the eventuality on the time axis, the phrase op zondag expresses a restriction on the proposition: it is specifically on Sundays that Marie gets up late (not on other days). We discuss the distribution and interpretation of temporal adverbials in more detail in Section V8.2.3.

Adjectives are not easily used as clause adverbials of time. Possible cases are vroegerin the past, tegenwoordignowadays and laterin the future. However, it is not clear whether these elements are really adjectives. For example, the element vroeger in (36) has a slightly different meaning than its attributive counterpart in zijn vroegere vrouwhis former wife and resembles the complement of the PP in We spraken over vroegerWe talked about the past. The fact that later can also be used as the complement of a PP, as in We sparen voor laterWe are saving (money) for later, suggests that we are dealing with nominal elements. We leave this to future research.

For completeness, note that the adverb vroegerin the past in (36a) is certainly not the comparative form of the adjective vroegearly, which is clear from the fact that vroeger cannot be replaced by the positive adjective vroeg or the superlative form het vroegst, as shown in (37a). Example (37b) shows that all these forms can easily occur as VP adverbials. Similar observations can be made for the adverb laterlater/in the future and the adjective laatlate.

Other possible cases are adverbs like zojuistjust now, strakslater/soon, gisterenyesterday, and morgentomorrow. The examples in (38) illustrate for straks that it can be used both as a clause adverbial and as a VP adverbial; cf.also the discussion of the examples in (19) from Section 30.2, sub III, which show that the position of the time adverb relative to the modal adverbs determines its construal as a clause or as a VP adverbial. Again, it is difficult to prove that we are dealing with adjectives.

The last set of adverbs that we will discuss here comprises emphasizers and amplifiers. Some examples are echttruly, absoluutabsolutely, and duidelijkclearly. The main function of these elements is to emphasize the truth of the statement or to scale up from a tacitly assumed norm. Some examples are given in (39). This class of adverbs is problematic because the paraphrases in the primed examples may seem somewhat artificial and do not fully cover the meaning of the primeless examples.

The examples in (40) show that adjectives of this kind can also be used attributively (cf. Section 23.3.5, sub II). Their adjectival status is therefore beyond doubt.

In fact, the adverbially and attributively used adjectives in (39) and (40) are quite close in meaning, in the sense that the adverbs in (39) are closely related to the noun phrases they precede. This may account for the fact that the paraphrases in the primed examples of (39) do not seem to fully capture the meaning of their primeless counterparts. One indication of this is that, unlike the clause adverbials discussed earlier, the emphasizer/amplifier must be left-adjacent to the predicative noun phrase in (39a) and the direct objects (39b&c). This contrast is illustrated in (41) with the modal adverb waarschijnlijk and the emphasizer absoluut from (39b).

How to rate this particular argument is perhaps not entirely clear: it may be that the unacceptability of (41b') is accidental. The unacceptability of the examples in (42) suggests that the emphasizer absoluut is only possible when the direct object is a non-specific indefinite noun phrase, and such noun phrases can never be placed before a clause adverbial; cf. *Jan zal een verhaal waarschijnlijk vertellenJan will probably tell a story. Nevertheless, the contrast between the doubly-primed examples in (41) strongly suggests that some kind of adjacency requirement is at work.

Further evidence that emphasizers and amplifiers must be left-adjacent to the nominal predicate or direct object comes from the double object constructions in (43). In (43a) the indirect object niemandnobody can follow the modal adverb waarschijnlijkprobably, while the placement of the indirect object after the emphasizer/amplifier absoluutabsolutely in (43b) is impossible with the intended reading; cf. (44c) below for further evidence.

Given that (43b) is acceptable if the adverb is interpreted as an emphasizer of the negation expressed by the pronoun niemand, perhaps we should conclude that these adverbs are not really clause adverbials but modifiers of non-specific indefinite noun phrases. If so, the het is adverb zo dat ... frame may not be a fully reliable test for detecting clause adverbials.

In the examples in the previous subsections, the clause adverbials occupy a position in the middle field of the clause. With the exception of the emphasizers/amplifiers in (44c), they can also be topicalized, i.e. placed in sentence-initial position. This is illustrated in (44a) for modal and subjective adverbs and in (44b) for frequency adverbs.

Placing the clause adverbials after the clause-final verb(s) is normally not an option, although it should be noted that example (45a), with a modal/subjective adverb, is acceptable if the clause-final verbs are followed by an intonation break; in this case the adverb is probably given as a (main-clause external) afterthought; cf. Section C37.3.

Some of the clause adverbials discussed above can co-occur in a single clause. Although the judgments are not always clear, the preferred order of these adverbs seems to be as indicated in (46); cf. Cinque (1990).

It is often not easy to combine a subjective and a modal adjective, but if it is possible, as with vrijwel zekeralmost certainly in (47a), the subjective adverb must precede the modal one. The subjective and modal adverbs precede the frequency adverbs, as shown in (47b) and (47c), respectively. The examples in (47d) show that the frequency adverbs in turn precede the emphasizers/amplifiers.

The examples in (48) show that the order in (46) must be preserved under topicalization; topicalization of one clause adverbial across another is blocked. We do not include examples with echt, since this element does not allow topicalization at all; cf. (44c).

For completeness, note that helaas can also be used as an interjection, as in (49). This case differs from (48a) in that helaas does not occupy the regular sentence-initial position, which is occupied by the subject het boek, but is main-clause external. This claim can be further supported by the fact that in this case helaas does not block the use of waarschijnlijk.