orelo

Straightforward body-part noun, and the usual accusative rule applies: en mian orelon with -n for whispering into it, en mia orelo without for something already sitting there. Orelringo is an earring, and orelumo the flap on a hat, both formed the obvious way. Where English says a good ear for music, Esperanto prefers bona muzika aŭdo, since the idiom does not carry over. Note that oreloj in the plural is unremarkable, unlike haroj, because ears come in a countable pair to begin with.