A coup d'état (pronounced /ku de'ta/), or simply coup, is the sudden overthrow of a government, often through illegal means by a part of the state establishment — mostly replacing just the high-level figures. It is also an example of political engineering. It can be (although not necessarily) violent, but it is different from a revolution, which is staged by a larger group and radically changes the political system through unconstitutional means.
The term is French for "a (sudden) blow (or strike) to a state" (literally, coup, hit, and état, state, ). The term coup can also be used in a casual sense to mean a gain in advantage of one nation or entity over another; e.g. an intelligence coup. By analogy, the term is also applied to corporations, etc; e.g. a boardroom coup.
Since the unsuccessful coup attempts of Wolfgang Kapp in 1920, and of Adolf Hitler in 1923, the Swiss German word "Putsch" (pronounced /pʊtʃ/) (originally coined with the Züriputsch of 1839) is often used also, even in French (such as the putsch of November 8, 1942 and the putsch of April 21, 1961, both in Algiers) and Russian (August Putsch in 1991), while the direct German translation is Staatsstreich.
Tactically, a coup usually involves control of some active portion of the military while neutralizing the remainder of a country's armed services. This active group captures or expels leaders, seizes physical control of important government offices, means of communication, and the physical infrastructure, such as streets and power plants. The coup succeeds if its opponents fail to dislodge the plotters, allowing them to consolidate their position, obtain the surrender or acquiescence of the populace and surviving armed forces, and claim legitimacy. Coups typically use the power of the existing government for its own takeover.