phi-features can also be considered the silent features that determine whether a root word is a noun or a verb. this is called the noun-verb distinction of distributed morphology. the table below describes how category classes are organized by their nominal or verbal characteristics. definitions for these four categories of predicates have been described as follows: a verbal predicate has a predicative use only; a nominal predicate can be used as the head of a term; an adjectival predicate can be used as a modifier of a nominal head; a preposition acts as a term-predicate for which the noun is still the head; an adverbial (not shown below) predicate can be used as a modifier of a non-nominal head.