base in

1. To root something in a particular thing, idea, or finding. In this usage, a noun or pronoun can be used between "base" and "in." There's no way this data is based in reality! When you stare up into the night sky, how can you feel any fear? All of our fears are based in earthly concerns anyway. You need to base your opinions in cold, hard facts.

2. To operate or function from a particular place. Our corporate headquarters is based in Spokane. The board of directors struck down our proposal for a new business based in Canada. If that conglomerate acquires our company, do you think we'll be based in a different city?

3. To locate something in a particular place. In this usage, a noun or pronoun can be used between "base" and "in." If we base our club in the English department office, then we can meet in there on Wednesday afternoons. Wait, the office of the mayor isn't based in City Hall? Don't you think it makes sense for the school newspaper to be based in the computer lab?

base in

1. To operate from some location. Used chiefly in the passive: Our company is based in Fresno.

2. To establish or found something in some location: We based our organization in the heart of the city.

3. To have something as a foundation or origin: The linguist based the analysis of the sentence structure in a standard framework.