* Collective Noun: When referring to the collection of food and household goods sold at a grocery store, it acts as a collective noun. For example: "I went to the store to buy some groceries."
* Common Noun: When referring to a single item sold at a grocery store, it acts as a common noun. For example: "I need to pick up some groceries, like milk and bread."
So, the type of noun "grocery" is depends on the context of the sentence.