The two voices may occur in any tense. The mood of a verb expresses the conditions under which an action or condition is taking place. Indicative and subjunctive can be in any tense, imperative only in the present tense. Verbs are also classified according to function. Action verbs show action or possession.
Action verbs are either transitive or intransitive.
Linking verbs show the condition of the subject. Auxiliary verbs, also called helping verbs, are used with other verbs to change the tense, voice, or condition of the verb. Conditional verbs are verbs conjugated with could, would, or should to show a possible condition. They may be in any tense. The principal parts of a verb are the four forms of the verb from which all forms of the verb can be made.