doceo

Doceo, docere, docui, doctum is second conjugation, and its defining feature is that it takes two accusatives: one for the person taught, one for the subject taught. Magister pueros grammaticam docet. Turn it passive and the person becomes the subject while the subject taught stays accusative: pueri grammaticam docentur, which looks impossible until you have seen it a few times.

The trap is doctus. The perfect participle hardened into an adjective meaning "learned, expert" centuries before the classical period, so doctus vir is a scholar, not "a man who has been taught". Doceo shares a root with disco, "to learn", and with decet; the English descendants are doctor, doctrine, document, docile and docent, all with the same double-edged idea of showing and being shown.