The word "sunset" is a noun. It refers to the daily event where the sun disappears below the horizon, marking the end of daylight. As a noun, it can function as the subject or object of a sentence, and it can be modified by adjectives or other descriptive words. For example:

• "The sunset was breathtaking." (Here, "sunset" is the subject of the sentence.)
• "We watched the beautiful sunset." (Here, "sunset" is the object of the verb "watched.")

Additionally, "sunset" can sometimes be used metaphorically or symbolically to represent endings, transitions, or the passage of time. For example:

• "The sunset of his career was marked by a final, triumphant performance."

In rare cases, "sunset" can also function as a verb, meaning to discontinue or phase out something, often used in business or legislative contexts. For example:

• "The company decided to sunset the old software by the end of the year."

However, its primary and most common usage is as a noun.