I'm doing translation exercises, and I translated "evince my opinion".
But the answer is "air my opinion"
I googled them, but there's no answer.
Here is the full sentence: Before airing my opinion, I will analyze the hot issue from diverse perspectives.
Is there any difference between "air one's opinion" and "evince one's opinion"?
Or are they just the same?
They are most certainly not the same, and while it is true that air is more colloquial than evince, that's a relatively small part of the difference.
Far more important is the idea of intentionality. If I air an opinion, it's because I want you to know what I think, and I've consciously written or said something to achieve that goal. I can evince an opinion, on the other hand, entirely by accident in any number of additional ways — through the work I do, the people I associate with, the web sites I visit, or through discourse apparently unrelated to the opinion in question.
The Oxford Dictionary definition of evince, for example, is simply to "reveal or indicate the presence of a quality or feeling." Who or what does the revealing is irrelevant.
To cite an example from today's news: In response to a journalist's question about China's trade practices, Donald Trump said the Chinese have broken every agreement, sought every unfair advantage, and and done whatever they can get away with. He doesn't blame them for that, but he'll put an end to it if he's elected.
Mr. Trump aired an opinion about trade policy. At the same time, he evinced an opinion about morality and proper behavior — the idea that it's not blameworthy to break agreements and do whatever you can get away with.
Finally, it should be noted that neither air nor evince is entirely right for the general case of "to make one's opinion known." To give, express, state, or share an opinion would all be more appropriate.
As noted by others, evince has a legalistic feel, while air implies a particular kind of discussion — involving both informality and a minimum level of disagreement. Grievances are on par with opinions in the word's Oxford Dictionary definition, and insubstantiality comes from the word itself.
Given that the context mentions hot issues and diverse perspectives, air may well be the best choice in this particular case. But generally speaking, you don't air an opinion if you're sure you're right, if you don't expect any pushback, or if you're more powerful than your listeners. You and your spouse might air opinions on household spending. But your doctor wouldn't air her opinion on how long you have to live, and judges don't air opinions in court.
The short answer is that "to air one's opinion is preferred over "to evince one's opinion" because the former is used much more often (common usage) than the latter. Additionally, the verb "to air" is more likely to be understood than the verb "to evince" which is formal and more likely to be spoken or written by lawyers, academics and the like.
I believe that there is also a nuanced difference in meaning between the two expressions. "To air" an opinion means to give one's opinion openly about someone or some thing which may or may not be accepted by third-parties, but "to evince" an opinion is, to my way of thinking, a more solid expression of one's opinion about someone or something, one that is more likely to be valid and accepted by third-parties.
TO AIR: (verb) To make opinions known to other people. (Cambridge Dictionary)
TO EVINCE: (verb) To show something clearly; to constitute outward evidence of (M-W)
