A government is the formal system and institutions through which a state exercises authority and makes decisions, while a regime refers to the particular way that system operates—its methods, ideology, and character in practice. The distinction centers on structure versus style.
Government is the neutral, institutional framework: the legislature, executive branch, courts, and bureaucracy that handle administration, lawmaking, and enforcement. Most stable states have a government regardless of how authoritarian or democratic it may be. The term focuses on how power is organized.
Regime typically describes the ruling system's character and approach: whether it's democratic, authoritarian, communist, military-controlled, or theocratic. It encompasses the implicit or explicit ideology guiding decisions and the actual methods of rule. A regime reflects how power is exercised. The same governmental structure can theoretically operate under different regimes—for instance, if a military coup replaces civilian leadership while keeping institutional titles intact.
In common usage, "government" leans formal and structural, while "regime" carries more evaluative weight, often implying the nature of rule. Academic and political discourse frequently use "regime" when discussing the character or legitimacy of a system, particularly in phrases like "authoritarian regime" or "communist regime." You'd less often hear "democratic regime" as naturally as "democratic government," though both are grammatically correct.
Historically, "regime" gained prominence describing how states actually governed versus their stated institutional design—the real power dynamics beneath formal structures. This makes it useful for analyzing whether a state's actual operations match its constitutional ideals.