Alternative Facts
I sometimes wonder what it would be like to an editor for the OED; to study etymology and semantics in such a fast-changing society must be both fascinating and daunting. If one starts with Oxford, one sees:
Fact: a thing that is indisputably the case.
Alternative: available as another possibility
As has been written, interpretation of facts can be wildly different. And statement of fact can be true, false, incomplete, misleading, etc., etc. In certain circumstances, two separate facts are interpreted to be oppositional, the inference being that one of them is not actually a fact (and, with statement of fact, that can often be the case). In other circumstances, both facts co-exist without such inference (light behaves like and particle and light behaves like a wave). Perhaps a science major will correct me vis a vis that light example (I'll not contest it), but it does raise the issue of absolutes. A thing that is (believed to be) indisputably the case in one age and one society, may not be so in another. It's easy to accept that "the sun revolves around the earth" is not, now, a fact, but it certainly was considered a fact by many, at one time.
As to whether Alternative Fact is ultimately regarded as an oxymoron, a useful concept, or a dangerous tool of propagandists, remains to be seen.