Which word from the diagram would be identified as an adjective?

The correct identification of an adjective from the provided options is based on the function each word serves in a sentence. Adjectives are words that describe or modify nouns, providing additional information about them.

In this context, the word "football" can function as a noun that describes a specific type of sport or activity. However, to fit the context of an adjective, it is often used in compound forms or phrases (like "football game"). The other words, such as "Monday," "for," and "yesterday," do not serve the role of describing or modifying nouns in the same way. "Monday" is a noun denoting a day of the week, "for" is a preposition that indicates relation, and "yesterday" indicates time, also functioning as a noun rather than providing descriptive qualities of another noun.

While "football" may not traditionally be categorized as an adjective in its standalone form, in phrases where it modifies another noun, that context creates a space where it can function in an adjectival capacity. This nuanced understanding allows "football" to be recognized in certain contexts as an adjective, aligning with the task of identifying which word from the given options serves an adjectival role.