The keyword phrase "September 11th, 2009" functions grammatically as a proper noun. It operates as a single, indivisible unit that names a specific and unique entity: a particular calendar date. This classification is the main point for determining its role within an article.
In linguistic analysis, a proper noun identifies a unique item, in contrast to a common noun, which refers to a general class of items. While the phrase is composed of individual components (the proper noun "September," the ordinal number "11th," and the proper noun "2009"), they combine to form a multi-word proper noun. Syntactically, the entire phrase can act as the subject of a sentence (e.g., "September 11th, 2009 was a Friday"), the object of a verb, or the object of a preposition, fulfilling the functional roles of a noun within a sentence structure.
Understanding this grammatical function is crucial because it dictates that the article's focus must be on the specific events, characteristics, or significance associated with that date. As a proper noun, the date serves as the central subject to be described, analyzed, or explained. The article's content would therefore revolve around defining what happened on, or what is notable about, this specific day, rather than using the date to modify another concept (as an adjective would) or to describe an action (as a verb would).
