A head (/hed/) or nucleus /nju:klɪəs/ (plural: nuclei /nju:klɪaɪ/) is either (1) the word of a phrase or (2) the stem of a compound which for both determines the syntactic category of that phrase (which may be a single word).
In English, for example:
- The head of the compound noun "handbag" is bag.
- The head of the noun phrase "large ladies who lunch" is ladies.
- The head of the adjective phrase “absolutely fabulous" is fabulous.
- The head of the adverb phrase "nearly completely" is completely.
- The head of the verb phrase "play football" is play.
- The head of the prepositional phrase "to the lighthouse" is to.
- The head of the wh- phrase "how often" is how.