LOL! Good, interesting topic. I have no idea, though. Probably “and” or something common like that. Then there’s the old F word. Haha. Just kidding. I’m not too bad with the F-bomb. 😉 What is yours, Pegasus?
If we don’t talk about the most commonly used words, then I think mine is (in writing) “The other day”, and “In this article” . I can’t say anything about a particular word. In spoken term, my most common word is “okay” as I don’t talk much in offline world.