When used as a keyword or title, the phrase "11 sep what happened" functions grammatically as a noun phrase or a nominal phrase. It acts as a single conceptual unit that names a topic of inquiry. In this capacity, the entire phrase serves as the subject matter for an article, rather than operating as a verb, adjective, or other part of speech.
This noun phrase is a composite of a temporal designator ("11 sep") and an embedded interrogative clause ("what happened"). The temporal element specifies the date, narrowing the context. The clause defines the nature of the information sought. When combined into a single keyword, the phrase transitions from a direct question into a label for a complex event and its associated details. Its grammatical function is analogous to other search terms that become topics, such as "how to change a tire" or "the causes of the French Revolution," where a procedural or interrogative phrase is treated as a singular noun concept.
The practical application of this grammatical analysis is structural. By identifying "11 sep what happened" as the subject (a noun phrase), the article's objective becomes clear: to provide the predicate. The content of the article must serve to define, explain, and elaborate upon this subject. The entire expository text is therefore an extended answer to the question that the keyword names, providing a detailed and factual account of the events associated with that specific date.
