(Related a bit to Difference between 实际, 现实, 确实, and 实在 I guess. Good to link to it for posterity.)
的确, 确实, 实在, 真正
My dictionaries all say that all four can be adverbs with a meaning of "really." That's not too helpful when you want to know which one you should use in which situation, and which one you can't use.
My problem culminated with this question: "没错，这本书__________是我的"
A: 的确, B： 实在, C： 真正
If they are all adverbs, and all can mean "really," then in my mind it's a trick question and I can use any. However ...
I asked a native Chinese speaker, and this is the explanation I received:
的确 and 确实 seem to have about the same meaning, both are adverbs and both seem to indicate a confirmation of a state, and rather than "really," makes more sense as "actually," e.g. somebody asks you to try this dish, because it tastes good, and you try it, then, "这个菜确实好吃" ~= "This dish actually is good!"
(Further to this, my dictionary says 确实 appears to be able to be used as an adjective also ... which wasn't covered in the explanation.)
实在 can be an adverb or an adjective, and makes more sense if you think of it as "honest(ly)" when you think something is very good or very bad.
真正 can be an adverb or an adjective, and makes more sense if you think of it as "true/truly".
There are a few areas that I've encountered in Chinese where the "English equivalent" isn't really the same, and there are certain rules and regulations that cover the Chinese word, but don't have the same distinction in English. I feel this is one of them.
I can see that 的确 will fit in the above question (It's not a mistake, this book actually is mine,) but going by the English explanations, to me, 真正 could fit too (It's not a mistake, this book truly is mine.) Oh, but ... "It's not a mistake, honestly, this book is mine"
Can anybody shed any light on this? I would honestly, actually be truly grateful.