What is the difference between in and at ?
While prepositions are inserted into all sorts of idioms that extend and contradict their basic sense, "in" and "at" correspond to the following primary local relations:
| A | "A is in B" (A is an entity, B is its container)
| "A is at B" (A is an entity, B is its location)
Again, though, remember that idiomatic usage may be very, very different!
Thank you very much