Noun and verb phrases are the two main constituents of English sentences. A noun phrase contains a head noun and any modifiers, and functions as a noun within the sentence. A verb phrase contains a head verb and any auxiliaries, modifiers, or complements, and expresses the action or state of being in the sentence. Many English sentences can be divided into a noun phrase and a verb phrase. The verb must agree with the subject noun or noun phrase in terms of number and person. Auxiliary verbs can affect subject-verb agreement when they precede the main verb.