"IF YOU SAY SO" is a great informal, colloquial phrase to know. You might hear it in movies, talk shows, podcasts, etc. We use this phrase when we don't agree with someone, but we don't want to argue. It may sound a bit rude because you are telling another person that you don't really believe them. A: The only way to become rich is to start an online business. B: If you say so. "B" doesn't agree with "A," but doesn't want to argue back. Maybe "B" isn't in the mood to argue, or "B" simply doesn't