What part of speech is "yesterday"?

"Yesterday" functions primarily as an adverb, indicating the time in which an action took place, specifically referring to the day prior to today. In sentences, it modifies verbs by providing context about when an event occurred. For example, in the sentence "I went to the store yesterday," "yesterday" tells us when the action of going to the store took place.

Though "yesterday" can also be used as a noun in certain contexts, such as when discussing a particular day in conversation or writing (e.g., "Yesterday was a great day"), its most common usage aligns with that of an adverb. The focus on how it modifies the action or state is key in determining its primary part of speech. Overall, understanding its role in a sentence supports recognizing it as an adverb rather than any of the other listed parts of speech.