Sentence Structure: Noun Phrases

All but the very briefest sentences contain noun phrases and academic writing is dense with these structures. So it is important to understand their structure when examining various types of sentences.

A noun phrase may consist of a single noun. In the sentence "Koalas can sleep up to 20 hours per day.", "Koalas" is the subject of the sentence; it is the head in a one-word noun phrase. Very often the head is accompanied by a determiner A word which is used with a noun and which limits the reference of the noun in a particular way. more... such as an article, a personal pronoun, a number, etc.

Head nouns can be premodified with adjectives, participial An adjective which is derived from a verb by using the -ed and -ing participle forms. more... modifiers and other nouns. They can also be postmodified with prepositional phrases A phrase consisting of a preposition and a complement (usually a noun phrase), often used as a post-modifier of a noun phrase. more..., relative clauses A clause which provides information about a preceding noun and which cannot exist on its own. more..., ed-clauses A participle clause (past participle) often used as a post-modifying clause of a noun phrase, and as part of an adverbial. more... and to-clauses A post-modifying to-infinitive clause providing extra information about a preceding noun phrase, or a noun complement to-clause. more....

Heads are obligatory elements, without which we wouldn't have a noun phrase. Determiners are almost always obligatory. Premodifiers and postmodifiers are mainly optional (but see the comments below). Complex noun phrases are common in academic writing so consult the noun premodification and postmodification pages.

Sometimes a sentence is not complete when a postmodifier is removed from a head. This is the case with the above example "the spread of disease". Without the prepositional postmodifier "of disease", "the spread" doesn't make sense (although it could in certain contexts). Similarly, the last example "one way that plants defend themselves" is incomplete without the relative clause "that plants defend themselves".

You can see further examples of noun phrase modification on the premodification with adjectives page, the premodification with nouns page, the complex noun premodification page, and the noun postmodification page.