The keyword term "September 11th plane crash" functions grammatically as a noun phrase. In this construction, the core element, or head noun, is "crash." This noun identifies the fundamental concept or event being discussed.
A detailed grammatical analysis reveals a hierarchy of modification within the phrase. The head noun "crash" is first modified by the noun adjunct "plane," which acts as an adjective to specify the type of crash. The resulting compound noun, "plane crash," is then further modified by the adjectival phrase "September 11th," which specifies the exact historical and temporal context of the event. Each preceding word serves to narrow the definition of the final noun.
Understanding this structure is crucial because it establishes the keyword as a specific entity. As a noun phrase, it can act as the subject, object, or complement within a sentence, allowing for the construction of clear, factual statements about the event itself. This grammatical function makes it the central point of reference around which all other information in the article is organized.
