ĉampiono

A borrowed root with a good story behind it. Latin campus was flat open ground, the field an army drilled on, and a campio was the man sent out onto it to fight in single combat for a side that stayed behind. Everything else the word does now comes off that: the medieval judicial duel, then the prize fighter, then the sporting title, and in English the further sense of championing a cause, which is still the same idea of fighting on somebody's behalf. The unglamorous branch of the same root gave us the university campus, a flat field on the edge of a town.

In Esperanto, ĉampiono is the title-holder. Ĉampioneco is the championship as a status and ĉampionado is the competition itself. Do not confuse it with heroo, which is about courage rather than about winning, or with venkinto, which is simply whoever won this particular thing: a venkinto won today, a ĉampiono holds the title.

Spelling note: it is ĉ with the hat, cxampiono in the x-system. There is no c version.