The term "11-Sep" functions grammatically as a proper noun. It serves as the specific name for a particular date, September 11, and by extension, refers to the series of terrorist attacks that occurred in the United States on that day in 2001. As a proper noun, it identifies a unique entity, similar to names like "World War II" or "the Great Depression."
In addition to its primary function as a proper noun, "11-Sep" is frequently used as a noun adjunct (or attributive noun), which means it acts as an adjective to modify another noun. In this role, it describes or categorizes the noun that follows it. For example, in the phrase "the 11-Sep attacks," the term "11-Sep" modifies "attacks." Similarly, in "the post-11-Sep era" or "the 11-Sep Commission," it qualifies the nouns "era" and "Commission," respectively, by linking them directly to the specific event.
Therefore, the grammatical role of "11-Sep" is context-dependent. While its core identity is that of a proper noun when it stands alone as the subject or object of a sentence (e.g., "The world changed after 11-Sep."), it adopts an adjectival function when placed directly before another noun to provide specification. The main point for an article would focus on its identity as a proper noun that names a significant historical event, recognizing its common adjectival use as a key syntactical feature.
