The term "September 11th incident" functions grammatically as a noun phrase. In this construction, "incident" is the head noun, which establishes the core part of speech. The preceding elements, "September 11th," act as modifiers that specify which incident is being referenced.
A detailed grammatical analysis reveals that "incident" is a common noun. The component "September 11th," a proper noun representing a specific date, serves as a pre-nominal modifier. This type of modifier, where a noun modifies another noun, is known as a noun adjunct or an attributive noun. Its function is adjectival, specifying the type or identity of the head noun. This structure is common in English for creating specific, descriptive terms (e.g., "space shuttle program," "income tax law"). The entire phrase refers to a single, specific event.
Recognizing this structure as a noun phrase is crucial for correct syntax and clarity. As a singular noun unit, it dictates subject-verb agreement (e.g., "The September 11th incident was..."). It also clarifies how to apply further modification; adjectives like "tragic" or "consequential" would precede the entire phrase ("the tragic September 11th incident") to modify the event as a whole. This grammatical understanding ensures the term is used precisely to maintain the article's focus on a singular, identifiable subject.
