Which one of six types of expository structure does this paragraph illustrate? A verbal may belong to one of three categories. It may be a participle, which is used only as an adjective. It may be a gerund, which always ends in -ing and functions as a noun. Finally, it may be an infinitive, which is preceded by to and functions as a noun, adjective, or even an adverb. Yet verbals still look very much like verbs.