After I published my article about being in/at school, one of my readers asked me about the difference between “in office” and “at office”.
What we would normally say is either in the office or at the office (notice the definite article). The preposition “in” in “I am in the office” implies that the office is a room and you are inside that room. The word “at”, on the other hand, conveys the general idea of the location of one's office and is often interchangeable with “at work”. To sum it up:
I am in my/the office. = My office is a room and I am in that room.
I am at my/the office. = I am somewhere near my office or in it. I am at work.
In office (without an article) means something quite different. We say that someone is “in office” when they work in an official position, usually for the state. For example, we could say:
Bill Clinton was in office from 1993 to 2001.
when referring to his presidential post.
Finally, at office (without an article) isn't common usage. If you feel the urge to say “at office”, say “at the office” instead:
I am not at the office right now.
I am not at office right now.
Here are a few more examples for all of the possible combinations:
I was in the office when you called.
She is not at the office today.
He has been in office for over ten years.
They will be at the office tomorrow morning.
Jakub Marian