The term "May Day" functions as a proper noun. As a proper noun, it names a specific holiday or day of observance, which falls on May 1st. Its grammatical role is analogous to other named days such as "Christmas Day" or "New Year's Eve." Consequently, both words in the phrase are capitalized to signify that they refer to a unique, singular entity rather than a generic day within the month of May.
Structurally, "May Day" is a compound noun, created by the combination of the proper noun "May" (the name of a month) and the common noun "day." Together, they form a new, specific name. While its primary function is as a noun, the term can also be used as a noun adjunct (or attributive noun), which acts adjectivally to modify another noun. For instance, in the phrase "a May Day rally," the term "May Day" describes the specific type of rally. The term itself refers to two distinct observances: a traditional European spring festival and International Workers' Day, a commemoration of the labor movement and workers' rights.
Understanding "May Day" as a proper noun is essential for correct usage in writing and communication. The capitalization signals to the reader that the reference is to the specific holiday with its associated cultural, seasonal, or political significance, not merely an arbitrary day in the month. This grammatical classification ensures precision and clarity, distinguishing the formal name of the observance from a simple description of a date.
