Erroneous is a careful, slightly formal way to say that an idea, a number, or a piece of information is wrong — not because someone is being naughty, but because the facts underneath it are not correct. An erroneous belief. Erroneous data. An erroneous conclusion. Courts, papers, and school essays like this word. It sits on the claim, not on the person: we say an erroneous report, not really “an erroneous man”. It is colder than “wrong” and a little more precise: it points at a false base. You would not usually call a tiny spelling slip erroneous in casual talk. Though actually, people do stretch it a little in news English, for any official statement that later turns out not to be true.