elokventa

The false seam first, because it is a good one. An Esperantist reading elokventa for the first time sees el- (out of), then reaches for okventa and finds nothing, because there is nothing there. The word is not built from Esperanto pieces at all. It is Latin eloquens borrowed whole: ex out plus loqui to speak, the present participle of speaking-out. The el at the front is Latin ex wearing an Esperanto disguise, and the coincidence is close enough to be genuinely misleading - which is exactly why it is worth stopping on. Take elokventa as one root and add endings only at the end.

What the Latin family gives you free. Loqui is behind English elocution, loquacious, colloquial, soliloquy, ventriloquist and circumlocution, and every one of those is about the mouth rather than the mind. That is the sense of the adjective: elokventa describes speech that carries, not thought that is correct. A dull truth is not elokventa; a well-turned falsehood can be.

Where it sits among its neighbours. Paroli is to speak, parolado at rank 525 is the speech itself, konvinki is to persuade, argumento at 1,478 is the reason offered, and lerta is skilful in any craft at all. Elokventa is narrower than all of them and specifically about delivery. The noun is elokventeco, the adverb elokvente, and the derived elokventulo is a fine speaker - though oratoro is the usual word for one by trade.

The English idiom transfers, which is not always true. You can say elokventa silento in Esperanto and be understood exactly as in English: an eloquent silence, a pause that argues. Zamenhof's own prose is full of the trick, and the Esperanto movement, which spent fifty years persuading people at congresses, had more use for this adjective than most.