We know by now what U sounds like. (Like the ‘oo’ in boo-boo.) The whole reason Ü––that letter I’ve been alluding to––exists is because of the letter G. It’s a correction (like the RR for R, like the QUE for CE).
Remember that G before E and I is a soft, aspirated sound—like the letter H in English. In the Spanish word general, the G sounds like the H in the English word ‘hello.’ Same thing happens in the word gitano.
The G before A, O, U, however, is pronounced hard, as in me gusta. That raised the question, how do I get a hard G sound before an E or I? And I said (in a previous post) you put a silent U in there: guerra, guitarra. In these combinations—gue, gui—the u makes no sound, it only serves to make the G hard before E and I. Guen—a fake word I just made up to illustrate the point—does not sound like the English name ‘Gwen.’ It sounds like Ghent (the city).
But this creates a new (and final) problem! What If I want it to sound like Gwen? That is, what if I want or need to pronounce the U? This is where la diéresis—the two dots over a U—is born. Only two combinations exist: güe and güi. In this case, it sounds like ‘gwe’ and ‘gwi.’ Now let’s look at this in action.
Vergüenza (‘ver-gwen-sa’) means shame. Verguenza (‘ver-gen-sa’) does not mean anything. And it doesn’t sound like anything, either. If you’re texting, auto-correct will automatically add the dots.
Pingüino (‘peen-gwee-no’) means penguin. Pinguino (‘peen-ghee-no’) doesn’t mean anything, but kind of sounds like pinga, which is Cuban slang for dick (among other things).
So the following combinations exist thanks to the G rules.
None of those combinations sound the same.
When I listen to Mexicans talk, they use güe a lot because it happens to be in the words güey and güero. Since I live in L.A., I hear güey all the time.
Let me repeat one more time: the ü only exists in the two combinations güe and güi. You should never write güa, güo, güu. Those don’t exist because they are unnecessary—the G would already be hard and the U would already be pronounced, like in the words guacamole and antiguo. (‘Guu’ isn’t a thing.)