The keyword phrase "september 11 2011" functions grammatically as a proper noun phrase. It acts as a single unit to name a specific, unique entity: a particular calendar date. As a noun, it can serve as the subject of a sentence, the object of a verb, or the object of a preposition.
A noun phrase is a group of words that functions in a sentence as a noun. In this case, the phrase combines a proper noun ("September") with two cardinal numbers ("11" and "2011") to form a specific name. For example, in the sentence, "September 11, 2011 was the tenth anniversary," the entire phrase serves as the subject. Similarly, in "The memorial was dedicated on September 11, 2011," the phrase is the object of the preposition "on." Its classification as a proper noun is due to its role in naming a specific, non-generic item.
While its primary part of speech is a noun phrase, its function within a sentence can vary. It can act as an adjectival phrase (specifically, a noun adjunct) when it modifies another noun, such as in "the September 11, 2011 memorial service." It can also function as an adverbial phrase of time, answering the question "when," as in "The museum opened September 11, 2011." Understanding this distinction between its fundamental classification (noun phrase) and its potential contextual roles (adjectival or adverbial) is critical for precise grammatical analysis.
