Intensive verbs ( sometimes referred to as relational, linking or copular) belong to a small group which include verbs like :be ,seem , appear,become , look and so on. What these verbs have in common is that what follows the verb in centence relates back to what precedes the verb for example :
Sally became a doctor
George is in the garden
Sue seems unhappy
In each of these example what is given after the verb relates back to the subject , describing their states.
The bit that comes after the verb function as the SUBJECT COMPLEMENT shorthand version sC.
Although the function of all bits are sC , the form are different
In the first example the noun phrase ( doctor ) function as sC
In the second example , a PP ( in the garden ) function as sC
In the third example , adjective phrase ( unhappy) function as Sc.
The intensive verbs are the only class of verb can be completed by an AP alone.
It is important to note that verbs in the intensive verb class, like transitive and ditransitive verbs are incomplete in their own. In other words some sorts of sC is obligatory.
The tree diagrams for the example are:
in terms of function the sentence patterns are the same:
Sally became a doctor
S---------P----------- SC
George is in the garden
S-------- P-----------sC
Sue seems unhappy
S------ P-----------sC