They’re both correct and have essentially the same meaning. As far as why the word “grocery” is singular in number 2, this is usually (but not always) the case when a noun is used to qualify another noun. For example, an egg-carton contains multiple eggs (for example, 12 eggs) — not just one. We do *not* say “an eggs-carton”.

Both

Hi Ensomih, Both are correct with only subtle emphasis but not meaning. In the first sentence, 'groceries' is a noun that is the food and supplies sold in a market. Number 2, 'grocery' is an adjective describing the type of shopping, telling us that you're going to buy food, rather than clothing, for instance. Hope this helps, e.