Noun phrases normally consist of a head noun, which is optionally modified ("premodified" if the modifier is placed before the noun; "postmodified" if the modifier is placed after the noun). Possible modifiers include:
Noun phrases can make use of an apposition structure. This means that the elements in the noun phrase are not in a head-modifier relationship, but in a relation of equality. An example of this is I, Caesar, declare ..., where "Caesar" and "I" do not modify each other.
The head of a noun phrase can be implied, as in "The Bold and the Beautiful" or Robin Hood's "rob from the rich and give to the poor"; an implied noun phrase is most commonly used as a generic plural referring to human beings. Another example of noun phrase with implied head is I choose the cheaper of the two.
That noun phrases can be headed by elements other than nouns—for instance, pronouns (They came) or determiners (I'll take these)—has given rise to the postulation of a determiner phrase instead of a noun phrase. The English language is not as permissive as some other languages, with regard to possible heads of noun phrases. German, for instance, allows adjectives as heads of noun phrases, as in Gib mir die Alten for Give me the olds (i.e. old ones).
In English, for some purposes, noun phrases can be treated as single grammatical units. This is most noticeable in the syntax of the English genitive case. In a phrase such as The king of Sparta's wife, the possessive clitic "-'s" is not added to the king who actually has the wife, but instead to Sparta, as the end of the whole phrase. The clitic modifies the entire phrase the king of Sparta.
Noun phrases are prototypically used for acts of reference as in "The blonde girl shouts" or "She kissed the man". Also possible, but found less often, is the use of noun phrases for predication, as in "Suzy is a blonde girl". Note that in English the use of the copula is indicates the use of a noun phrase as predicate, but other languages may not require the use of the copula. Finally, noun phrases are used for identifications like "The murderer was the butler", where no ascription is taking place. The possibility for a noun phrase to play the role of subject and predicate leads to the constructions of syllogisms.