The keyword term "september 11th 23 years" functions as a compound noun phrase. It is not a single part of speech but a combination of elements that act together as a single noun. In this construction, "September 11th" serves as a noun adjunct, modifying the core noun phrase "23 years" to specify a particular duration of time thematically linked to that specific date.
Grammatically, the phrase is composed of two distinct parts. The first, "September 11th," is a proper noun identifying a specific historical date. When placed before another noun, it takes on an adjectival role, specifying which 23-year period is under discussion. The second part, "23 years," is a standard noun phrase indicating a quantity of time. The combination creates a condensed, specific identifier for a concept: the 23-year period following, or defined by, the events of September 11th. This structure is common in headlines and search terms where conciseness is prioritized over full syntactical sentences (e.g., omitting prepositions like "of" or "since").
Understanding this phrase as a noun is crucial because it establishes the primary subject of the article. It is not describing an action (a verb) or simply qualifying another term (an adjective). As the central noun, it can be the subject of a sentence (e.g., "[September 11th 23 years] represents a generation of change.") or the object of analysis (e.g., "The article examines [September 11th 23 years]."). This grammatical function dictates that the article's main point will be to define, analyze, or explore this specific, named period of time as a singular topic.
