The keyword phrase "patriots day boston marathon" functions grammatically as a compound proper noun. It acts as a single, specific name for a unique cultural and athletic event, combining the name of a holiday ("Patriots' Day") and a race ("Boston Marathon") into one distinct identifier that serves as the subject.
This classification is determined by analyzing its constituent parts. "Patriots' Day" is a proper noun naming a specific civic holiday. "Boston Marathon" is a proper noun naming a specific annual race. When used consecutively, they form a unified noun phrase where the entire string of words is treated as the formal name for the event. The phrase operates as a single conceptual unit, naming a particular entity rather than describing a general category.
Recognizing the phrase as a compound proper noun is the foundational point for the article. This grammatical function dictates that the subject is a singular, specific entity with its own unique identity, history, and context. All content should therefore treat the term as the specific subject to be analyzed and explained, rather than as a descriptive adjectival phrase modifying an unstated noun.
