Adverbial adjectives vs. adjective-adverbs

In German linguistics, words like langsam in der Hund läuft langsam (‘the dog walks slowly’) are traditionally classified as ‘adverbially used adjectives’. We argue instead that they should be classified as adverbs, regularly converted from adjectives. We show that classical arguments for labeling them adjectives are spurious, because they need to resort to decontextualization which is not a legitimate strategy for defining part-of-speech. An argument for treating them as adverbs is that their semantic contribution is comparable to that of regular adverbs and not to that of prototypical adjectives, in that they do not predicate over an entity variable, but over another predicate or an event variable. Such semantic differences usually justify classification in different parts-of-speech. Some relic unambiguous adverb forms still survive; they show distributional constraints that can be explained by their inability to predicate over entities.