Are you always saying things such as “at the morning” and “in the beach?” Well, hate to tell you, but that’s incorrect. Although they’re not watertight, it helps if you know these easy rules.
At, in, on for Place
Use at when you mean that a person or a thing is at a certain place, such as a building, but it doesn’t matter where they are in the building.
at the office
at the airport
Use in when you want to say that someone or something is in a larger place, such as a city or country.
in the forest
in the kitchen
The difference between at and in
With at and in you can express whether you’re talking about the place in general, or inside it.
Compare: at the movie theater vs. in the movie theater
Look at how this is used:
Where did Lucian go? I think he’s at the movie theater with his girlfriend.
Where did Lucian say he’d meet his girlfriend? He told her to wait for him in the movie theater. (which means inside).
Use on when someone or something is on an area, or is hanging against something.
on the wall
on the floor
on the second floor
on the back page of the newspaper
Part 2 of this article is about at, in and on for time expressions.