The keyword term functions grammatically as a noun phrase. The core component of this phrase is the noun "day," which serves as the head of the phrase, identifying the central concept being discussed.
In this construction, the head noun "day" is pre-modified by two other elements that provide more specific information. The word "special" is an adjective that describes a quality or characteristic of the day. The component "11 sep" functions as a noun adjunct, which is a noun or date used adjectivally to specify which particular day is being referenced. Together, these modifiers narrow the focus from any day to a specific, significant date.
Understanding this grammatical function is critical for proper syntactical integration into an article. As a noun phrase, it can act as the subject of a sentence (e.g., "The 11 Sep special day is a time for reflection."), the direct object of a verb (e.g., "We commemorate the 11 Sep special day."), or the object of a preposition, ensuring it is used as a cohesive conceptual unit within the text.
