the head parameter deals with the way in which phrases themselves are structured. each phrase has a central element, called a head; in the case of a noun-phrase, the head is the noun, in the case of a verb-phrase it is the verb, in the case of a prepositional-phrase, it is the preposition, and so on. one dimension along which languages vary is the position of the head in relation to other elements inside the phrase, called complements. for example, in the noun-phrase the girl with blue trousers, the head-noun girl appears to the left of the complement with blue trousers; in the verb-phrase hit the girl, the head hit appears to the left of its complement the girl;similarly, in the prepositional-phrase with blue trousers, the head with is on the left of its complement blue trousers. in fact english is a head-first language, because the head of the phrase always appears before its complements. Japanese, on the other hand, is a head-last language, because the complements precede the head inside phrase.