What is an example of the sort of things that children learn nonverbally? One of the simplest examples to observe, analyze, and discuss is the way people use clothing and bodily ornamentation to communicate.

In my opinion, that 'to communicate' is adverbial, but my book says it's adjectival, like that of 'water to drink'.

Is it really so?
No, it's not really so.

It's an adverbial of purpose. It tells why people use clothing and bodily ornamentation.

Thanks, Jim!