Specifier

In X-bar theory in linguistics, specifiers, head words, and complements together form phrases. Specifiers differ from complements because they are not sisters of the head, but rather sisters of the phrase formed by the head and the complement. In English, some example of specifiers are determiners such as the, no, some, every, and possessives such as John's and my mother's, which can precede noun phrases. Adverbial phrases can be preceded by degree words such as very, extremely, rather and quite.