I think that it sounds pretty much the same but I could see those nunances: Common: It's what people would usually do. Like common knowledge, knowledge that everyone has. When you say something is common, it's something most people would probably do. Normal: it's the standard way, how things were supposed to be. If we take a video game with different levels of difficulty, "normal" would be the normal choice, but people will commonly pick easy or hard. So if you say something was normal, it was "how it was supposed to be", I guess, with no surprises. Ordinary: It's something that happens pretty much everyday. Again, it can be related to you or in general. Like, ordinary people have breakfast in the morning, nothing surprising there. So I guess you could switch them pretty much anytime you want and it would make sense. They all have that "unsurprising" feeling. To my hear, the sentence: "I think this phrase is very... common" is correct because it conveys the meaning that most people would use that sentence. Hope it helps, as always, this is what I think. maybe I am wrong ^^

Hi, they all more or less mean the same thing, there are just certain times when we use them and other times when we don't! In this example we would only say "I think this phrase is very common in daily life". Common here means there are lots of different cases in which you could say the phrase, as in it's found in lots of different scenarios. "Ordinary" generally means that the thing you are describing is just standard, it doesn't necessarily mean it's found all over the place. As in if there were only five of this kind of jewel in the world, you could say one was "ordinary", meaning it's similar to the other ones. However, if you said "common", it means it's found in many different places and there are probably far more than five of them. "Normal" is very similar to ordinary. It means the thing you are describing represents the qualities found in all the others. e.g. "他是很正常的男人“。意思就是“他不是奇怪的男人”。Hope this helps! 祝你好运！