An ideology is a fairly complete set of beliefs that a political or economic system sits on — or that quietly steers how people behave. Capitalism and communism are the textbook examples, though actually people also talk about the ideology of a company or a school when they mean its deep, not-always-spoken rules. The word was borrowed from French idéologie, coined in 1796 by Antoine Destutt de Tracy, who first meant something more like “the science of ideas”. It is related to the English word idea, but it was not built from that English word; they share older roots. Napoleon later used a related word as an insult for his opponents, and that helped push ideology toward today’s sense: a doctrine, a package of beliefs, not a calm study. In ordinary talk it can sound heavy; in news and essays it is everywhere.