Is the letter
r in Esperanto pronounced like
غ in Arabic? Or like
r in French?
Is the letter
The most common pronunciation that most people strive for is like the rr in Spanish (ie, it is trilled).
However in practice many people have difficulty with this and it’s not uncommon to hear the French or English r. It doesn’t really pose any problems to understanding. In the official source of Esperanto, The Fundamento, it’s not really clear which pronunciation is actually official, if any, because each translation of it tends to say the r is pronounced the same as in the target language. In general as long as the sound is consistent and cleary distinguishable it doesn’t really matter too much how it’s pronounced.
PMEG has a more complete description of the pronunciation.
A few years ago a student asked Bertilo Wennergren whether it is correct to say vi ĉiam duobla-ro-igas ĉion to a person who usually says veterro (alveolar trill) instead of vetero (alveolar tap). Although the question was about the use of ig, Bertilo thought the student was asking him whether it is correct to say veterro instead of vetero, and he answered that it is not too important whether you use a long or a short r sound. You can watch it here.
Watching that video, it's pretty obvious to me that Bertilo tends to pronounce the r like in vetero, not veterro. For instance, he says koloro, not kolorro; Esperanto, not Esperranto, and so forth. On the other hand, if the word starts with an r he tends to pronounce it like in veterro; for example he says rruĝa, not ruĝa. It seems to me that this is a general tendency among many Esperanto speakers, i.e., long r if the word starts with it, short r otherwise. Just to clarify, by long r I mean an alveolar trill and by short r I mean an alveolar tap. Those are, by the way, the two r sounds used in modern Spanish.
In my opinion the multiple ways Esperanto speakers pronounce the r challenges the idea of one letter, one sound, and I don't mean this is something bad or good, I'm just saying that theory does not always match reality. Listen carefully to how Juliette Ternant pronounces the r in this interview. She pronounces the words Esperanto kaj mirigita like vetero (i.e. like a Spanish single r, which is an alveolar tap), but in the words gramatikaj and problemoj she pronounces it like a French r. Nevertheless, her Esperanto sounds to me very good and it flows in a natural and understandable way.
Anyway, if you're interested in learning how to trill/roll the r in Esperanto like they do in Spanish, there are lots of tips on YouTube. Don't forget to have fun and remember that in Esperanto there are no rules about this, only tendencies and recommendations (en la praktiko ĉiu litero varias en sia elparolo).