At home / in the hospital, etc.
We say that somebody is at home / at work:
– I’ll be at work until 5:30, but I’ll be at home all evening.
You can also say be/stay home (without at):
– You can stop by anytime. I’ll be home all evening.
We say that somebody is in the hospital / in prison / in jail”
– Kim is not living at home. She’s away at college.
But use in school/college to say what someone is doing:
– Amy works at t band and her brother is in medical school. (= he’s studying medicine)
At a party / at a concert, etc.
We say that somebody is at an event (at a party / at a conference, etc.):
– Were there many people at the party / at the meeting / at the wedding?
– I saw Steve at a tennis match / at a concert on Saturday.
In and at for buildings
You can often use in or at with buildings. For example, you can eat in a restaurant or at a restaurant;you can buy something in a supermarket or at a supermarket.
We usually say at where an event takes place (for example, a concert, a movie, a party, a meeting):
– We went to a concert at Lincoln Center.
– The meeting took place at the company’s headquarters in New York.
We say at the station / at the airport:
– Don’t meet me at the station. I can get a taxi.
We say at somebody’s house:
– I was at Sue’s house last night. or I was at Sue’s last night.
Also at the doctor’s, at the hairdresser’s, etc.
We use in when we are thinking about the building itself. Compare:
– We had dinner at the hotel. but
All the rooms in the hotel have air conditioning. (not at the hotel)
– I was at Sue’s (house) last night. but
It’s always cold in Sue’s house. The heating doesn’t work very well. (not at Sue’s house)
In and at for towns, etc.
We normally use in with cities, towns, and villages:
– Sam’s parents live in St.Louis. (not at St.Louis)
– The Louvre is a famous art museum in Paris. (not at Paris)
But you can use at or in when you think of the place as a point or station on a trip:
– Does this train stop at (or in) Denver? (= at the Denver station)
– We stopped at (or in) a small town on the way to Denver.
On a bus / in a car, etc.
We usually say on a bus / on a train / on a place / on a ship but in a car / in a taxi:
– The bus was very full. There were too many people on it.
– Mary arrived in a taxi.
We say on a bike (= bicycle) / on a motorcycle / on a house:
– Jane passed me on her bike.