The term "september 11 federal holiday" is a noun phrase, with "holiday" as the head noun and "september 11" and "federal" acting as modifiers. Grammatically, it refers to the concept of establishing the anniversary of the September 11th attacks as a national holiday recognized by the United States federal government. However, this status does not currently exist in U.S. law.
The official designation for this day is Patriot Day, established by Public Law 107-89 on December 18, 2001. It is a National Day of Service and Remembrance. This classification is distinct from a federal holiday. Federal holidays, such as New Year's Day or Independence Day, typically mandate the closure of non-essential federal government offices, postal services, and federally chartered banks. In contrast, a national day of observance like Patriot Day calls for specific commemorative acts, such as flying the U.S. flag at half-staff and observing a moment of silence, but does not include widespread business and government closures.
Therefore, the use of the noun phrase signifies a misunderstanding of the day's legal and civic status. The key distinction is functional: while the day holds immense national significance, its commemoration is intended to be one of solemn remembrance, service, and reflection within the context of a normal workday, rather than a day of leave from work and school as provided by an official federal holiday.