Three Branches of Government

I know what the three branches of government are, and what they do, but for school I'm supposed to say what the three branches of government are and use one word to describe what they do. (Seriously? Only one word?) So the thing is I can't think of one word to describe what they do. I didn't think it would be this hard! Please tell me a word to describe each of them (or at least one of them!) Please no swear words in the answers or comments. Thanks! :D