eleganta

The -ant- here is not a participle, and that is the whole trap. Esperanto's present active participle really is -ant-: kuranta is running, skribanta is writing, parolanta is speaking. So eleg-ant-a looks like a perfectly formed participle of a verb elegi. It is not. There is no elegi, there is no root eleg-, and the ending is not doing participle work. The root is elegant-, borrowed whole, and the final -a is the ordinary adjective ending.

Except that in Latin it was a participle, which is the good part of the story. Elegans is the present participle of eligere, to pick out - the same legere that gives elekti, to choose, and English select, elect and intelligent. So an elegant person is originally a choosing person, somebody who picks carefully. And in early Latin that was not a compliment: elegans meant fastidious, fussy, a bit precious, the sort of person who sends the wine back. It softened over a century or two into praise for good taste, and it is the praise that reached us.

That is a pattern worth naming, because it recurs across the borrowed vocabulary: the seam is real in the source language and dead in this one.Incidento six ranks earlier is the same shape - a Latin participle frozen into an Esperanto root. Enjoy the etymology, do not build with it.

What it actually means in use. Eleganta covers the same ground as the English adjective and no more:

• Of clothes and people: well-dressed, stylish, unfussy. Eleganta robo, eleganta viro.
• Of a solution, a proof or a piece of code: economical and satisfying. Eleganta solvo, eleganta pruvo. This sense is fully alive in Esperanto and is what you will meet in technical writing.
• Of movement or manners: graceful. Eleganta danco.

The adverb is elegante, the noun is eleganteco, and the opposite is maleleganta - or, more often, just senguste, tastelessly. Note the distance from bela: a thing can be bela without being eleganta, because bela is about beauty and eleganta is about restraint. A sunset is bela. It is not eleganta.