I. The verb
II. Basic structure of VPs
Example: VP [easily opened the door with her credit card]
III. Complements and adjuncts in the VP
VPs are constituents whose heads are verbs. Verbs can be classified according to whether they require any VP-internal NP. Traditionally, three classes of verbs are distinguished: transitive, ditransitive and intransitive verbs.
If a VP has a transitive verb as its head, one NP (i.e. the direct object) is required: the verb takes an NP-complement; e.g. Sally [opened the door]. If a VP has a ditransitive verb as its head, two NPs or an NP and a PP (i.e. the direct and the indirect object) are required: the verb takes two complements; e.g. Sally [gave the money to John]. If a VP has an intransitive verb as its head, no complement is allowed; e.g. Sally [laughed].
The obligatory constituents that are required by a verb (i.e. subject and complements) are called its arguments. Thus, a sentence like Sally opened the door contains two arguments: the subject NP Sally is one argument and the object NP the door is the second argument of the verb open. The verb's specification for the number of arguments it requires is called its argument structure or (referring to the semantic relationships between verbs and their arguments) thematic structure. These semantic relationships are described in terms of thematic roles or theta roles. Thus, the verb open takes two arguments to which it assigns a theta role: it assigns the role AGENT to the subject argument of the sentence, and the role THEME to the object argument. In general, we can say that a verb theta-marks it arguments. The component of the grammar that regulates the assignment of thematic roles is called theta theory. (For more information on thematic relations, see the page from the Semantics section of ELLO).
Adjuncts, such as PPs providing information about the manner, time, or place of the event expressed in the sentences, are not required by the verb but may be included optionally; e.g. with her credit card and on Monday in the sentence Sally [opened the door with her credit card on Monday]. Adjuncts may also appear in pre-verbal position, such as easily in the sentence Sally [easily opened the door with her credit card].
IV. Specifiers in the VP
According to the so-called VP (internal subject hypothesis) it is the subject that originates in the specifier position of VP where it receives a theta role. The subject is subsequently raised into the specifier position of IP (subject-to-subject raising), leaving a co-indexed trace. For further information read the page on INFL as a functional head.
In the text above we refer to constituents of the type [determiner + noun] (e.g. the door) as NPs. In a more recent analysis, determiners are considered to be the head (D°) of a determiner phrase (DP), and the noun functions as its NP-complement.
For further information on DPs click here.