Past tense verbs indicate actions or events that occurred in the past. They can be either regular or irregular. When a past tense verb is regular, they are formed with the verb root (or base form) of a verb plus the "d" or "ed" ending; and when it is irregular, the verb does not end with "d" or "ed" and does not follow any particular patter, for example, <em>thought, known, sat, </em>and<em> slept</em> are all irregular verbs.
The verb "occurred" is a regular verb in the past tense because it is formed with the base form "occur" plus the "ed" ending. Other examples of regular verbs in the past are <em>purred, believed, typed, walked </em>and<em> moved.</em>
