While plagiarism is a recurrent problem, the main purpose of references to the scholarly literature is to indicate your being in touch with that literature. Definitions and notions are sophisticated, and it is likely that even an authoritative dictionary won't settle the meaning of terms in scholarly discourse. (My favorite example is the use of "collaboration" as in collaborative planning. Used in that context, its meaning is clear. But all I can think of is Nazi collaborators, highlighted for me by the famous Robert Capa photograph of an alleged French collaborator after WWII, her hair cut off. I should note there is now some criticism of these photograph and what was done. There are many such photographs.)
Critical thinking skills mean that you not only know how to make an argument, but you indicate you are aware of the problems with your argument. That may be explicit, it may be in notes. You know that history is likely to be presented with a certain bias (but professional historians readily acknowledge their orientations, and that is part of their argument), so that simple stories of progress are surely nonsense. You know that an argument that has an uncritical or unscholarly section is likely to fall apart no matter how strong are the other parts.
Moreover, in scholarship and in critical thinking the idea that one might quantify everything, or most things, is generally thought to be a mistake. Judgments can be justified, but not always or often quantified. On the other hand, Kahneman's Thinking Fast and Thinking Slow points out how often quantified judgments might well be powerful, but what is then quantified is very different than what most people pay attention to. (Think of the movie Moneyball.) Clinical judgments might well be replaced by statistical tests, the diagnosing psychologist by an Minnesota Multiphasic Personality Inventory (MMPI) or its more recent successors.
One of the most interesting phenomena these days are automatic grading of essay questions, and the correspondence of those grades with those of readers of the essays. What you need to attend to are the poorly corresponding cases, to find out if you are missing important stuff: very poor essays that pass, and excellent essays that are missed.
More generally, you want to ask;
Who says? Who disagrees? Why?
Are there interesting analogies with other cases?
What are the specific meanings of notions in this field or discipline?
Here is what I wrote to one student: