Clarify the difference between 間違い and 違い

Question

I thought that 違う{ちがう} means "to be difference" and 間違う{まちがう} mean "to be mistaken". But i'm pretty sure I heard 違う used as "its mistake" or "it's not right" in anime.

Also, a friend told me that in now people use 違う more to with mistake context. Could you please help me clarify this?

Answer 1

You can interpret ちがう as "to be different from the correct one." Actually まちがう is a portmanteau word(紛う{まがう}+ちがう). 紛うmeans "mistake". So as you know まちがう have the meaning of mistaking.