The phrase "11 sep festivo" functions as a noun phrase. In this context, it acts as a single conceptual unit to name a specific event: a public holiday occurring on September 11th. The entire term serves as the name of the topic, much like a proper noun.
Grammatically, the phrase is a condensed construction. "11 sep" is a specific date acting as a nominal identifier. The word "festivo" is a Spanish term that can be either an adjective meaning "festive" or a noun meaning "holiday." In this phrase, it can be interpreted as a noun being modified by the date ("the holiday of September 11th") or as an adjective modifying an implied noun, such as "da" ("the festive day of September 11th"). In either analytical path, the functional outcome is the same: the combination creates a cohesive noun phrase that refers to a specific entity.
For the purpose of an article, treating this keyword as a noun phrase is the most practical and accurate approach. This classification allows it to serve as the subject of a sentence (e.g., "11 sep festivo is a significant date in Catalonia"), the object of a verb, or the object of a preposition. This understanding is crucial for building grammatically correct sentences around the main point of the article.
