Specifier

In X-bar theory in linguistics, specifiers, head words, and complements together form phrases. Specifiers differ from complements because they precede the head and are not subcategorized for. For example, noun phrases can be preceded by words (sometimes phrases) like: the, no, some, every, John's, my mother's. Adverbial phrases can be preceded by degree words such as: very, extremely, rather, quite.