In some languages, including English, noun phrases are required to be "completed" with a
determiner in many contexts, and thus a distinction is made in syntactic analysis between phrases that have received their required determiner (such as
the big house), and those in which the determiner is lacking (such as
big house). The situation is complicated by the fact that in some contexts a noun phrase may nonetheless be used without a determiner (as in
I like big houses); in this case the phrase may be described as having a "null determiner". (Situations in which this is possible depend on the rules of the language in question; for English, see
English articles.) In the original
X-bar theory, the two respective types of entity are called noun phrase (NP) and N-bar (N, N). Thus in the sentence
Here is the big house, both
house and
big house are N-bars, while
the big house is a noun phrase. In the sentence
I like big houses, both
houses and
big houses are N-bars, but
big houses also functions as a noun phrase (in this case without an explicit determiner). In some modern theories of syntax, however, what are called "noun phrases" above are no longer considered to be headed by a noun, but by the determiner (which may be null), and they are thus called
determiner phrases (DP) instead of noun phrases. (In some accounts that take this approach, the constituent lacking the determiner – that called N-bar above – may be referred to as a noun phrase.) This analysis of noun phrases is widely referred to as the
DP hypothesis. It has been the preferred analysis of noun phrases in the
minimalist program from its start (since the early 1990s), though the arguments in its favor tend to be theory-internal. By taking the determiner, a function word, to be head over the noun, a structure is established that is analogous to the structure of the
finite clause, with a
complementizer. Apart from the minimalist program, however, the DP hypothesis is rejected by most other modern theories of syntax and grammar, in part because these theories lack the relevant functional categories. Dependency grammars, for instance, almost all assume the traditional NP analysis of noun phrases. For illustrations of different analyses of noun phrases depending on whether the DP hypothesis is rejected or accepted, see the next section. ==Tree representations==