The term "11 sep world" functions as a noun phrase. In this construction, the head word is the noun "world." The preceding element, "11 sep" (an abbreviation for the date September 11th), acts as a noun adjunct or attributive noun. A noun adjunct is a noun that modifies another noun, functioning similarly to an adjective by specifying a particular type or context.
Grammatically, the core element is the noun "world," but its meaning is fundamentally altered by the modifier "11 sep." This modifier pinpoints a specific historical demarcation, transforming the general concept of "the world" into the specific geopolitical, social, and cultural landscape that emerged after the events of September 11, 2001. The structure creates a compound concept, where the date doesn't just describe the world but redefines it, signifying a distinct historical epoch.
For the purpose of an article, the main point is this specific, qualified noun concept. The focus should be on the characteristics of the global environment as defined and shaped by the 9/11 attacks. The keyword directs the article to analyze a particular state of beingthe post-9/11 erarather than the date or the world as separate entities. Therefore, the entire phrase should be treated as a single conceptual unit representing a distinct historical paradigm.