As far as we can tell, the most obviously tragic routes to language death – genocide and fatal diseases introduced by foreigners – are rare in human history. Most languages become endangered through processes that are fatal only to the languages, not to their speakers. In this chapter we explore social, economic, and political causes of endangerment, among them the prestige of a victorious invader's language; the expedience of pleasing conquerors by speaking their language; the need to know a particular language in order to get a better job, or any job; ethnically mixed school systems and workplaces that promote linguistic assimilation; and government efforts to force assimilation to a dominant culture, as seen for instance in the residential schools in the U.S., Canada, and Australia that actively suppressed indigenous languages. In the penultimate section I discuss the effects of standardizing a language on overall linguistic diversity – in particular the decline and loss of newly nonstandard dialects. Finally, I discuss factors that help to preserve a language from endangerment, most prominently official state support, economic power of the speakers, large numbers of speakers of all ages (and without noticeable reduction over time), and language loyalty.