We already noted that the first noun phrase in our examples is often referred to as SUBJECT of the sentence. Similarly the noun phrase that follows a verb is often called the DIRECT OBJECT. A transitive verb is said to take a direct object, while an intransitive verb does not. The similarity between transitive and intransitive verbs leads us to classify them in the same general category: VERBS. We have considered verbs from a purely structural point of view. In traditional grammar, however, they are defined in terms of meaning: A verb is a word that expresses action or being.
We can revise our verb-phrase rule to account for the existence of both intransitive and transitive verbs:
VP -----> VI
VP -----> VT NP
Examples:
The rain continued.
The rain annoyed Paul.