Word choices can take the sting out of a disagreement
Sara is teaching tact and open-mindedness early:
Can a word be a hack? If it can, I propose "mistaken." We've introduced this one to our 2 year old, and it just feels right. We use it to admit we are wrong. We use it when she is mistaken about something. And recently, she's started using it with her classmates a daycare ("Anthony said this is 4 (holding up 5 fingers), but I told him he was mistaken, this is five."). It's a nice word, with a neutral sound to it, but even better is that it replaces the word "wrong." It invites you to explore what you thought was the case, but now someone is telling you may not be. Isn't that a lovely philosophy; so much better than a black and white "wrong."
I love the idea of giving kids an education in how words can "feel," not just what they mean. In an effort to keep the focus on the behavior and not the person, we often talk to our kids about certain actions or words as "not being friendly" rather than being "mean." One must avoid veering into "parentspeak" and using vague words kids don't understand (with "appropriate" sitting at the top of my list) -- but I truly believe that choosing our words carefully makes a huge difference in social learning.