A verb is a word that describes an action, occurrence, or state of being. It is one of the main parts of speech in English grammar and is used to convey the action or state of the subject in a sentence. Verbs can be used in different tenses, such as past, present, and future, and can also be modified by auxiliary verbs to express different aspects or moods. Examples of verbs include "run," "eat," "sleep," "is," and "will."