Phrasal verbs and collocations

As always with English, there are lots of exceptions to these rules. Firstly, phrasal verbs do not follow these rules. For instance to "get on" with someone means to be friendly with them. To "get in" or "get into" is regularly used to mean arrive, and to "get at" something means to imply something indirectly. However, these prepositions don't follow the rules of the triangle.

Second is collocations. These are words that are commonly found together. For instance, we can be "interested in" something or "focus on" something. These prepositions don't follow the triangle either.

There's not always only one right answer.

If we take for instance, my office. That's the room that I'm writing this "in" right now. We can definitely use "in" because it's an enclosed location. It has a roof and four walls. However, it's also a specific location. So I might say something like, "I'll meet you AT my office". However, I could also say I'll meet you IN my office". Both would be fine. We could do the same with "train station". This is both an enclosed location and a specific location. So we could use either "in" or "at". Whilst one is a lot more popular than the other, neither is incorrect.