Regime, Regimen, Regiment

Regime: The word regime (occasionally spelled "régime") refers to a set of conditions, most often of a political nature. It may also be used synonymously with regimen, for example in the phrases "exercise regime" or "medical regime."

Regimen: a regulated course, as of diet, exercise, or manner of living, intended to preserve or restore health or to attain some result.

Regiment: A regiment is a military unit, composed of variable numbers of battalions, commanded by a Colonel.