As is said here, there are three types of adjectives/adverbs in German:
- Predicative adjectives: Der Clown ist lustig.
- Adverbial adjectives/adverbs: Der Clown springt lustig herum.
- Attributive adjectives: Er ist ein sehr lustiger Clown.
In English, some adjectives are only predicative, not attributive, for example, sick: I am sick, but not a sick man. Are there such adjectives in German?
Also, most German predicative/attributive adjectives can be used as adverbs, if it makes sense. But, probably, not all of them?