What part of speech is "witnessed"?

The term "witnessed" is a verb because it signifies an action, specifically the act of observing or seeing something happen. In English grammar, verbs are words that convey actions, occurrences, or states of being. In this context, "witnessed" denotes the action of seeing an event or situation unfold, which aligns it with the characteristics of a verb.

Other parts of speech such as nouns, adjectives, and adverbs serve different grammatical functions. Nouns represent people, places, or things; adjectives describe or modify nouns; and adverbs modify verbs, adjectives, or other adverbs. Since "witnessed" relates to an action rather than a person, thing, or modifier, it firmly classifies as a verb.