I've been looking for an answer to my question for a long time, but I've got no results. I've read plenty of grammar books but haven't found the straight and clear answer for the question in the topic "Why do you say "to/at/in the zoo, to/at/in the shop, to/at/in the river, to/at/in the cinema, to/on the roller coaster etc.? Why don't you use indefinite articles when a place, a thing (like "roller coaster) is not specific?"
Can somebody explain to me why we still say "I go to the shop", "I'am at the shop" even if we don't go to or at a specific shop or we mention it for the first time? Can we say "I go to a shop", "I am at a shop"? Why do we still say "I go to the zoo", "I am at the zoo" even if we don't go to or at a specific zoo, or we mention it for the first time? Why don't we say "I'm at a zoo", "I go to a zoo"? The same questions about to/at/in the river, to/at/in the cinema, to/on the roller coaster etc.
I'm really struggling to understand it. I think I'm not alone.
When answering the question, please, don't use things like "we just use". I need a clear, grammarly based explanation with all the details.
Or tell me about the books that I could use to clarify the matter by myself.
Sorry for the grammar and punctuation mistakes in my text, no one is perfect.
Thanks to everybody who is trying to answer the question.