Even Greener Pastures

I don't think there is a rule, not even an informal one.  Off the top of my head I can't think of a regional accent that would claim a rule, nor an immigrant group that would struggle over it.  I can't remember being corrected on my usage of either.  I never think about it but I know I use both.

It has to be whatever is easiest for your mouth to pronounce in the particular sentence, as the word is everywhere.  English did win the lottery in the "easiest definite article" category.  Certainly not like Italian (shudder).

Sofia, the rule is: "thuh" + consonant, but "thee" + vowel, resp. vowel sound, e.g. "thee" before "honesty", as the "h" has to be dropped, but "thuh" one (because although the word "one" technically starts with a vowel, it doesn't start with a vowel sound).
Apart from that, "thee" may also be used for emphasis, for example if somebody says "Johnny Depp was at our hotel last week" and you respond with "What? You mean, THEE Johnny Depp?"

Yes, the „the“ does have the pronunciation differences Alharacas described. I learned that myself only a few weeks ago in the videos I watched. I was unaware of the distinction until then, but always used it.

Native speakers aren’t taught or corrected on the pronunciation of their own language (we should be so we would then know how we are pronouncing words, and it´s a super-simple rule). But, we just distinguish these things based on what sounds right.

Alharacas is it really a published "rule"?  I know it is certainly entirely unconscious in my speaking and I cannot remember it being taught in school.

Steve I disagree with what you said - native speakers are indeed taught pronunciation and grammar.  I remember struggling through the mire of it in Jr High School.  I also think that once you reach school age there is a lot of peer pressure to conform to speaking like everyone else.  That is where regional accents come from.

I think we ought to hire schoolchildren in our target language to follow us around and make fun of our speaking mistakes.  That is the only way to have a language program that truly meets the advertising - "Learn your target language intuitively, just like a child does"!

I remember from Jr High:
1.  I hated grammar
2.  I hated the kids who liked grammar

I remember diagramming sentences.  I even challenged the teacher on it "Why are we learning this stuff?"  "No one makes sentences like this".  Of course that didn't go over well.

Now speech class I liked.  The Speech teacher would come to class every year and take us one by one into the hall and have us say a series of tounge twisters.  She was listening for stutters, speech impediments and lisps.  I had a lisp in first grade, said th instead of s sometimes.  So a couple of times a week we would leave regular class and go play speech games with the cute speech teacher.  She also gave us candy.

I was cured pretty quick, but soon learned how to talk with a lisp whenever she was around.  I was able to keep up that con well into 3rd grade.

I can't really prove it right now, but yes, I seem to remember it was mentioned in one of the Cambridge books I had to use in class. Plus, if I hadn't had to teach it, I don't think I'd have been able to come up with the rule at the drop of a hat. I'm not surprised you can't remember being taught about this in school, though. As you said, you use whatever's easiest on the tongue. It's just that this fits nicely into a rule (for once).

Further question: is it wrong to say thuh onion, thuh elevator?

I really did sort of glaze over in school when the teacher would bring up a "rule" in English.  In English every spelling and grammar rule has so many exceptions that I felt it useless to memorize the rules.

Alharacas
"Be careful what you wish for. This may be exactly what you're going to get once you've retired to that Italian village of your dreams."
Thanks ever so much for deflating my romantic dreams of an idyllic Italian retirement.  Why can't you be a stereotypical German and remain reticent?

@Sofia
The children wont be mean to me will they?

No matter.  I will just do the same thing I did when the kids made fun of me in grammar school.  Sell them candy at a discount.

@Sofia

You can say „thuh elevator“ or „thuh onion“ and I`m sure many people do, but you would have to use the glottal stop to avoid running the words together. I`ve frankly never heard anyone run the words together without the stop. I doubt anyone even knows how many people say „thee onion/elevator“ vs „thuh onion/elevator“ and I`m quite sure few Americans even know or hear the difference, it´s that subtle.

This is one of those things native speakers are never taught (except for maybe in speech therapy class). Native speakers are not taught pronunciation. In fact, they know it before they even get to school. Only when they get to school and speech impediments are noticed (like a lisp) are they taught to overcome it.

I have no idea when I say „thee onion“ vs. „thuh onion“ and in my entire life have never even thought about it until now. I doubt it`s a hard and fast rule of any sort.

@Neal

If you had the lisp as a little kid, which is common, then you would have, and should have, been taken aside and given speech therapy classes for that. I don`t know what the percentage is of children with this problem is, but it`s certainly not uncommon. I never had any speech impediments as a child, but I know of a few kids who did. My cousin, who was my age, had a speech problem of some kind (I`ve forgotten exactly now what it was), and I think it was probably the lisp as you mentioned, but after speech therapy in school, he got over it too. I wonder if that´s the only sound the few kids with speech impediments have in English, the lisp. With Castellon Spanish or Icelandic, since at least Icelandic has the TH sound in just about every word and sometimes it appears multiple times in one word, I have to wonder if their children have this same problem.

The only thing I recall is my mom constantly correcting my younger sister to not say „It happened on accident“ and instead to say, „it happened BY accident.“ I assume my sister just picked the „on accident“ up off the street. A lot to do over one lousy preposition.

I never had pronunciation or language problems of any kind, for some reason, at school. Languages just came to me easily (even the dreaded high school Spanish).

So as to English grammar, sure it was taught it and the „rules“ were quickly forgotten once the class was over. I was never taught pronunciation. Like Noam Chomsky says, „If someone has to teach you the grammar of your own language, the odds are pretty good that what you are being taught is false. Otherwise you wouldn`t have to be taught it. No one teaches you your own language, any more than they teach you how to see. It´s something that just grows in your head....children already speak their own language before they even get to school.“