The keyword term functions as a noun phrase. The head word, which establishes the primary part of speech for the main point, is "observance." As a noun, "observance" refers to an act, ceremony, or custom of commemorating an event or following a tradition. The component "September 11th" serves as a proper noun acting as an adjective or noun adjunct, modifying "observance" to specify the particular event being commemorated.
In this grammatical structure, "September 11th" precisely defines the type of observance being discussed. This analysis is crucial because it distinguishes the topic from the verb form, "to observe," which would focus on the action of watching or noticing. By centering on the noun "observance," the subject is framed as the established practices, rituals, and formal acts of remembrance. The grammatical core is the commemoration itself, not the historical date or the general action of remembering.
Therefore, the main point of an article using this keyword must be the ceremonies and traditions associated with remembering the attacks. The focus is not on the historical event itself, but on the subsequent and ongoing human response in the form of memorials, services, and rituals. This grammatical determination directs the article's content toward the methods and significance of the commemoration.
