The keyword phrase "september 11th in 2001" functions grammatically as a noun phrase. It acts as a single unit to name a specific, unique historical event and a particular point in time, much like a proper noun such as "The Great Depression" or "World War II."
A detailed analysis of its structure reveals that the core of the phrase is the date "september 11th," which serves as a proper noun. The subsequent prepositional phrase "in 2001" acts as an adjectival modifier, specifying which particular September 11th is the subject. The entire construction, however, is used collectively as a noun. For example, in a sentence like, "[September 11th in 2001] changed global politics," the entire phrase serves as the subject. While it can also be used adjectivally to modify another noun (e.g., "the September 11th in 2001 attacks"), its primary function when standing alone as the keyword topic is nominal.
Identifying the term as a noun phrase is crucial because it establishes the event itself as the central subject of the article. This allows it to be the grammatical subject or object of sentences, enabling direct discussion about its causes, effects, and significance. Treating it as a core noun concept provides a clear and stable anchor for all related descriptions, analyses, and arguments within the text.
