The keyword term functions grammatically as a noun phrase. It operates as a single unit to name a specific concept: the official day of remembrance. The core of this phrase is the head noun "day," which is modified by the other words to create a precise designation.
A detailed breakdown of the phrase reveals its components. "Patriot Day" is a proper noun, in which "Patriot" serves as an attributive noun (a noun used as an adjective) to specify the type of "Day." The prepositional phrase "for September 11th" acts as a post-modifier, providing essential clarification and distinguishing this observance from any other event with a similar name. The entire constructionhead noun plus its modifiersconstitutes a complete noun phrase.
Understanding this grammatical classification is critical for its use as a main point. As a noun phrase, it can serve as the subject of a sentence (e.g., "[The term] is a day of service..."), the direct object of a verb (e.g., "The nation observes [the term]..."), or the object of a preposition. This allows the article to be constructed around this specific entity, treating it as the central topic to be defined, described, and explained, thereby ensuring it remains the focal point of the content.
