O artigo THE e suas particularidades

I was on my class of basic English when a student asked what was the difference between 'go to the school' and 'go to school', and I really stopped for a while, and he continued saying 'because I see here "go to the library". What are the cases I have to use THE and the cases I don't?'

I really didn't feel my world falling apart, because as continuous learners that we are, we don't know every single detail about English, but as a teacher I told him I was going to take a look at it. I did some research and thing is that:

- THE is used for things determined or already talked about. Ex:

Ted: Marcus, Alice is my friend and I like her so much. (After two minutes, Alice comes to the place this conversation is being held).
Ted: Marcus, this is THE girl I told you I liked so much;

- THE is used to emphasize the noun that is after it or to joke acidly. Ex:

I am going to THE school I always liked. (My school s***s.)
I am THE teacher. (Such a confident person.)
She is THE most prepared person for this job. (This is, as you know, the superlative case in which we use THE plus the adverb intensifying the adjective 'prepared' that is in his turn giving quality to the noun 'person'.)


- THE is used for something or someone commonly known or irrelevant among the speakers(in conversations), readers(when something is mentioned, for example, in the page you just flipped), etc. Ex:

THE thing is coming. (In this case, THING is pejoratively referring to a person known between the speakers);
She's going to see the dentist. (In this case we don't have to say the dentist's name, because it's known by the patient and irrelevant for me)

- THE is used after a preposition to indicate you're going to somewhere as a visitor, or that you're going to receive, see, suffer something after arriving at this place. Ex:

I am going to THE library. (I am going to look for some subject on the books I am going to find there)

NOTE!!!!: If I use some sentence indicating a location without the, it means I am going to make an action, perform an action relating to the noun I'm getting referred as a place. Ex:

I am going to work. (I am going to my office to perform my work, develop what I'm in my company for.)
She is going to the dentist. (She's going to see the dentist, she's going to get some assistance from the dentist).

- And some say that THE is linked to THAT, as the Oxford Dictionary says here about THE http://oxforddictionaries.com/view/entr ... _us1298132 and about THAT http://oxforddictionaries.com/view/entr ... _us1298122 and take a look at ORIGIN. And this is why some people and up on this article I say THE is for something already talked about, and that in Portuguese and English we can also refer to it adding THAT. Ex:

Marcus, this is THE girl I told you I liked so much;
Marcus, this is That girl I told you I liked so much!