The keyword phrase "September 11 Memorial" functions as a proper noun. The main point or head of this phrase is the word "Memorial," which is a noun.
In this grammatical construction, "Memorial" is the core noun that identifies the subject as a place or structure created to commemorate an event. The preceding words, "September 11," act as an adjectival modifier (specifically, a noun adjunct). This modifier specifies which particular memorial is being referred to, distinguishing it from any other memorial. Therefore, while the entire phrase is a specific name (a proper noun), its fundamental grammatical role is determined by the head noun "Memorial."
Identifying "Memorial" as the key noun is crucial because it establishes the article's subject as a tangible entitya specific, named location. This determines how the phrase will function within sentences, typically as a subject or an object, and directs the focus of the content towards describing this physical place and its significance.
