Here's why:
* Common nouns refer to general, non-specific people, places, or things.
* "Harvest" refers to the general act of gathering crops or the crops themselves, not a specific instance.
For example, you might say:
* "The harvest was plentiful this year." (general act of gathering)
* "We had a good harvest of apples." (general group of apples)
To make "harvest" specific, you would need to make it a proper noun, like:
* "The Harvest Festival is next week." (specific event)