<R> is such a weird concept across languages. Speakers of lots of different languages seem to have a concept of <R>, despite those languages using all kinds of different writing systems.

Language learners use sounds from their own native language, and they're mostly understood by others. For sounds like /t/ and /g/ and /f/, where the differences between accents are relatively minor, it's not surprising that we can understand people with foreign accents.

But for <R> sounds, it boggles my mind how we can all understand each other. Because <R> can stand for So. Many. Different. Things!!!

- alveolar trill [r] (Most of Eastern Europe, Spanish, Arabic)
- alveolar tap [ɾ] (Spanish, Arabic, Scots, Japanese)
- uvular fricatives and trills [ʀ~ʁ~χ] (Parisian French, Standard German, Danish)
- uvular approximant [ɰ̙~ʁ̞] (Modern Hebrew, sometimes)
- labial approximant(?) [w] (English, almost everywhere, sometimes)
- alveolar approximant [ɹ] (English, almost everywhere, sometimes; Dutch, sometimes)
- retroflex approximant [ɻ~ɻʷ~ɻ̃ʷ] (Southern US English)
- lateral approximant [l] (Japanese, sometimes)
- glottal fricative [h~ɦ] (Portuguese, sometimes)
- weird tongue-folded vowel thingy [ɚ~ɚ̃] (Most US English, sometimes)
- literally just the vowel [a~ɐ] (Standard German, Danish)
- <R> itself has no sound, but makes the previous vowel longer (Most non-American English, most of the time; Danish, most of the time)
- <R> itself has no sound, but makes the next consonant after it a retroflex consonant (Swedish, sometimes)

Like, what? How are these in any way all "the same"???? Actually not even that! How are these all "vaguely related" even????