Appositions can appear in a variety of forms: as shown in example (25), they can take the form of an AP, a PP, a relative clause or a noun phrase; cf. Quirk et al. (1985/1991) and Heringa (2012). Appositions are similar to non-restrictive modifiers in that they usually follow the noun phrase they modify. In speech, they are easily recognized by a very distinct intonation break (a pause and usually a falling intonation that is much more pronounced than in the case of non-restrictive modifiers), which clearly separates them from both the preceding and following material and emphasizes their parenthetical nature. In written language, they are separated from the noun phrase by a comma or surrounded by dashes or parentheses. To avoid confusion with non-restrictive modifiers, we will use dashes in the following discussion.

In traditional grammar, the term apposition is often restricted to noun phrases such as een jong, verlegen meisje in (25d), which can never be interpreted as a restrictive or non-restrictive modifier. However, we see no principled reason not to extend the term to cases like (25a-c).

In speech, appositions are typically used as corrections or clarifications; they are added as an afterthought, providing additional information that the speaker realizes—a little late—that the addressee might need. Since true corrections and clarifications occur only in spontaneous speech, appositions are used in other types of text to characterize certain information as backgrounded but at the same time important enough to be mentioned. The additional information provided by the apposition can relate to the information of the modified noun phrase in several ways.

The examples given earlier show that appositions usually follow the DP to which they are related. At first glance, adjectival and participial appositions occasionally appear in prenominal position, as in the examples in (32). However, these constructions are largely confined to written language (or scripted speech). In spoken language, it is not easy to pronounce the examples with the given intonation contour: the intonation break preceding the noun is especially difficult to realize in a natural way. It is therefore possible that we are simply dealing with non-restrictive prenominal modifiers that the writer has placed within dashes or parentheses to achieve a certain stylistic effect. Note that if we were dealing with appositions in these examples, we would have to drop our earlier assumption in (24) that appositions are not within DP; cf. the discussion of the position of non-restrictive modifiers below example (19) in Section 16.1.2, sub II.

Sometimes it is possible to extrapose the apposition. In this case, the information is very clearly added as an afterthought, either for the purpose of correcting or clarifying the information given within the related noun phrase, or for the purpose of giving additional information about the referent of that noun phrase; cf. Section C37.3, sub IV.

The discussion of appositions in this section seems to justify the conclusion that, although they bear some resemblance to modifiers, appositions should be considered as a separate category. Given their parenthetical nature, as well as the syntactic behavior they exhibit, it seems that they must be placed outside the DP. It has been popular to analyze appositions as reduced relative clauses: this may be supported by the fact that some of the cases above involve adverbial markers and can indeed be paraphrased by means of non-reduced relative clauses. Note, however, that example (29c), which involves an attribution relation, and the examples in (30) and (31), which involve an inclusion relation, cannot be paraphrased in this way; cf. also McCawley (1998: §13) for discussion. Van de Velde (2009:80ff.) gives a number of arguments, partly based on comparative evidence, for the view that appositions are in fact clause-external elements; we refer the reader to Chapter V13 for a more general discussion of such elements.