certamen

Certamen, certaminis, n. Third declension neuter, from certo, certare, to contend, with the -men suffix that turns an action into a thing, the same one that makes flumen out of fluo.

Its range is wider than the military words. Proelium and pugna are strictly fighting; certamen keeps the underlying image of two sides straining against each other, so it serves equally for the games, a lawsuit, a debate in the senate and a pitched battle. It looks like certus, "certain", and the two are genuine cousins through cerno, to decide, but a certamen is the fight over a decision rather than the settled result. Nothing about it is certain until it ends.