noun A word that represents a person, place, thing, or idea. In this case, 'hold' can be a noun when referring to a grip or control.
preposition A word that shows the relationship between a noun (or pronoun) and other words in a sentence. In this case, 'by' is a preposition indicating the method or means by which something is held.
noun something that belongs to oneself
adjective referring to something belonging to oneself
noun a person who owns something
adverb modifies a verb, adjective, or another adverb by providing information on how, when, where, or to what extent something is done