The keyword term is a construct combining a proper noun phrase ("September 11th") and a verb ("happen"). The main point or thematic subject is the proper noun, "September 11th". This noun identifies a specific historical event, which is the core subject of inquiry. The verb merely specifies the action or state of being about which information is being sought.
In a detailed grammatical analysis, "September 11th" functions as the subject. It is a nominal phrase that names a unique, globally recognized event. The word "happen" is an intransitive verb presented in its base form, which is common in search queries where standard syntax and conjugation are omitted. This structure, [Noun + Verb], creates a verbless clause that functions as a command or request for information regarding the occurrence of the event named by the noun.
For the purpose of an article, this grammatical analysis dictates that the primary focus must be the proper noun. The noun establishes the "what" of the articlethe event itself. The verb "happen" directs the article's purpose, which is to explain the details, timeline, and nature of that event's occurrence. Therefore, the noun is the foundational element around which all explanatory content is built.
