When do you use "the" and when do you not use "the" in a sentence?

I intuitively know but don't know how to explain.

I'm trying to explain this concept to an ESL student.

closed as too broad by Laurel, Jason Bassford, Dan Bron, John Lawler, Scott Oct 31 '18 at 3:37

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • This question is entirely too broad to answer. If you can edit this into a specific question, please do so. Otherwise, you could try checking the dictionary or perhaps browsing the [definite-articles] tag. – Laurel Oct 30 '18 at 23:31
  • The thing to tell an ESL student is that there is no single rule. Instead, articles (and prepositions, and conjunctions, and other little words) are the gears in the machinery of grammar, and there are dozens (maybe hundreds) of special, idiomatic, non-logical, arbitrary rules, each covering a special context. For instance, the use of articles before disease names is quite idiosyncratic, but typical of the kinds of rules that native speakers have learned by heart as children. – John Lawler Oct 31 '18 at 0:27