What is the predicate noun or adjective in sentence dancing one of oldest forms communication?

The sentence "Dancing is one of the oldest forms of communication" is a bit tricky because it seems to have both a predicate noun and a predicate adjective!

Here's the breakdown:

* Predicate Noun: The phrase "one of the oldest forms of communication" acts as the predicate nominative or predicate noun. It renames the subject, "Dancing".

* Predicate Adjective: You could also argue that "oldest" acts as a predicate adjective. It describes the subject "Dancing" by telling us about its age.

So, technically, both phrases are grammatically correct, but the predicate noun phrase carries the main meaning of the sentence.