Properties of the head:
- syntax: the syntactic category of the head determines the category of the phrase
- morphology: morphological marking of the entire constituent is often realized at the head (finiteness, tense, agreement, case, number, gender, ...)
- semantics: the head determines the 'kind' of objects described.
- clause (S):
In HPSG the sentence is a projection of the verb. Consequently the VP that is the sister of the subject is the head of the local tree dominated by S.
- clause (S'), also called CP:
An S' is introduced by a complementizer or a subordinate conjunction. In many syntactic theories this function word is consider the head of S'. (This is true for both GB and HPSG as presented in this ELLO module.)
- For the VP, NP, PP, AP, and AdvP the highest verb, noun, preposition, adjective or adverb of the respective phrase is the head.
- In the case of non-branching trees the single daughter is considered the head.
We have marked the head in the following tree diagram: