Copyright does not protect ideas, systems, information, inventions, or anything else that isn't expression which has been fixed in a tangible medium.
One well-regarded case which you might read concerning this is Baker v. Selden, 101 U.S. 99 (1880), in which the Supreme Court decided a case between the makers of two ledger books, where it was fairly obvious that the defendant's book copied the bookkeeping system found in the plaintiff's book. While the Supreme Court explained that the essay outlining the system for bookeeping which prefaced the Plaintiff's book of ledger forms was undoubtedly the protected by copyright, all the Defendant had really copied was the system itself in printing his own ledger forms to be used with that system. The Court explained that the system itself was not protected by copyright, and as such, the ledger forms which were necessary to the use of that system were also not protected.
Anyhow, it's a good read, and one of the cases taught in law school to explain what we know as the idea-expression dichotomy, which is the principle that copyright law only really protects expression, and not the bare idea or information underlying the expression.
So, for example, if you're using 'linguistic ideas' or 'linguistics information' in your language, and not any particular expression of that information, then you're almost certainly safe. For example, if you read a paper on how allative cases are constructed in the Basque language, and you decide that you'd like to include something similar in your own constructed language, you'd be able to do so, since you wouldn't really be using anything expressive. On the other hand, there might be some argument that a constructed language such as Quenya or Klingon could be said to be expressive enough to qualify for copyright protection (and I honestly don't know the answer to whether or not they would qualify, but I have heard that there's some debate over the issue), and so one might need to exercise some caution in creating something identifiably derivative from either.
Keeping with Tolkien a bit: You can write stories about elves, wizards, dwarves, and such without having to worry about infringing the copyright in J.R.R. Tolkien's works, but if you write a story which actually uses Tolkien's characters and extensively quotes from his works, you could find yourself in some hot water.
And I would say that, aside from the cases in which a court has definitively ruled that there is fair use (such as in recording a copy of a television broadcast so as to be able to view that broadcast later), the fair use doctrine can be somewhat tough to nail down, but it's generally thought to be pretty safe to take examples from those cases and analogize to similar proposed uses. So, since Betamax VCR recording of broadcast television were deemed legal in Sony Corp. of America v. Universal City Studios, Inc., 464 U.S. 417 (1984), it's been widely agreed that the same holds true for other recording formats which are to be used for personal or household purposes, such as DVRs.
Finally, I'd say that your uses are most likely fair use, and that's assuming your use is actually copying or creating derivative works based on some copyrightable expression, and not just copying some idea or information. The fair use exception was carved out of copyright explicitly in order to allow critical, educational, and research uses of copyrighted works, and the courts are in general very deferential to the view that those types of uses are almost certain to be fair use (since they're spelled out right in the statute).