Verb

Verbs are traditionally described as 'doing' or 'action' words. Verbs are an OPEN and MAJOR WORD CLASS and comprise two basic types: MAIN and AUXILIARY VERBS. A verb can be the only unit in a clause e.g. Wait! Verbs are marked for TENSE and show AGREEMENT with the SUBJECT.
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Verb Phrase

This is a phrase whose Head word is a verb.

Vocative

A vocative is a noun phrase which directly addresses someone. For example, Bob, can I have a word? I need that book now, Sarah.

Voice

Voice refers to the ACTIVE/PASSIVE distinction. For example, Linda bought a Porsche is active, whereas The Porsche was bought by Linda is its passive counterpart.
See also