What I meant by registers was different relationships/pronouns/verb endings to indicate different levels of politeness. I should have written honorifics. Japanese and Korean have these. Chinese languages don't.

I thought of mentioning tones, but they're not as much of a problem for learners as they're made out to be. Cantonese has seven tones. However, there are no word pairs where the only difference is that one has a high level tone where the other has a high falling tone.

As an English speaker, the entire concept of tones is more than a little daunting.

On a lesser scale, the hardest thing about learning German, as, again, an English speaker, but one who had poor grammar instruction and no grounding in Latin, the idea of cases for verbs and pronouns was... weird.

Tones become part of the pronunciation of the word (though it's maddeningly easy to think of it as separate, with your English-brain saying that they can be safely ignored).

I've had a bunch of German, and just passing contact with Latin, but a lot of German grammar started making a lot more sense when I started thinking of those languages as similar in a sense, because of declension.

> Tones become part of the pronunciation of the word

True that. Also, it's just a different use of tone - English uses tone to differentiate questions from statements, and to otherwise add meaning to words/sentences. There are other mechanisms for that in Chinese dialects.

The best explanation I've heard of tones is the different pronunciations of "really" in "Really?" "Really!" "Really hungry" "Really good" etc

Yes about the intonation of the word. The difference is that that "really" would mean "mom", "stupid", "really", "nothing" according to the tone. Some embarrassing mistakes.

Well, the previous poster's examples of "really" could be defined like this, based on interpretation of their intonation:

"Really?": Convince me; "Really!": I'm indignant on your behalf; "Really hungry": exceptionally [hungry]; "Really good": average.